Inclusion Criteria:
* Aged ≥18 years and ≤75 years, male or female, at the time of signing the ICF;
* Meeting the Hanifin \& Rajka diagnostic criteria for atopic dermatitis (AD), with a documented history of AD of at least 6 months prior to screening (participants with prior diagnoses described as "eczema", "dermatitis" or similar terms, who have a disease history meeting the inclusion criteria and can provide corresponding medical records, such as inpatient or outpatient charts, and are judged by the investigator to have AD at screening, may be enrolled);
* Having a vIGA-AD score of 2 or 3 at the baseline visit;
* Having an EASI score between 5 and 21 (inclusive) at baseline;
* Having AD-affected lesion areas (excluding lesions on the scalp, palms, and soles, but including facial lesions) involving 5%-25% of body surface area (BSA) at the baseline visit, and the lesion sites are suitable for topical treatment;
* Female participants of childbearing potential and male participants who have not undergone vasectomy must agree to use effective contraception during the study period and for 3 months after the last dose, and must fully understand the study content;
* Voluntarily participation in the study with signed informed consent form.
Exclusion Criteria:
* Presence of infection in the AD lesion area requiring topical or systemic anti-infective therapy, or requiring very potent or potent topical corticosteroids or systemic corticosteroids to control AD disease activity;
* Presence of other active inflammatory skin diseases (e.g., psoriasis, seborrheic dermatitis, lupus, etc.) that, in the investigator's judgment, would interfere with the assessment of response to study drugs;
* Presence of scarring, tattoos, or hyperpigmentation in the AD lesion area that, in the investigator's judgment, would interfere with the assessment of response to study drugs;
* Presence of systemic or local active infection within 14 days prior to randomization;
* At screening, laboratory tests showing ALT or AST \>2 × the upper limit of normal, or severe renal insufficiency (creatinine clearance \<30 mL/min calculated using the Cockcroft-Gault formula; one repeat test is allowed, and participants who still fail to meet the inclusion criteria after repeat testing will be excluded);
* Unwillingness to limit excessive ultraviolet exposure (e.g., sunbathing and/or use of tanning devices) during the study;
* History of tuberculosis or active tuberculosis (presence of signs or symptoms suggestive of active tuberculosis as judged by the investigator at screening); Note: Participants with a prior history of tuberculosis may be screened if, in the investigator's assessment, the condition has been cured for at least 3 years prior to randomization.
* Prior or suspected human immunodeficiency virus (HIV) infection, or positive HIV antibody at screening; or positive hepatitis B surface antigen (HbsAg); or positive hepatitis B core antibody (HBcAb) with hepatitis B virus deoxyribonucleic acid (HBV-DNA) above the upper limit of normal; or positive hepatitis C virus (HCV) antibody with HCV RNA above the upper limit of normal; or positive treponemal-specific antibody test (participants with a positive treponemal-specific antibody test may be enrolled if the non-treponemal antibody test is negative and, based on clinical judgment, the infection is considered inactive);
* Receipt of the following treatments within the specified time periods prior to baseline evaluation:
1. Treatment with biologic agents (including intravenous immunoglobulin) within 12 weeks or 5 half-lives (whichever is longer);
2. Use of JAK inhibitors, systemic corticosteroids and/or immunosuppressants, or undergoing sunbathing, phototherapy (including ultraviolet therapy, photochemotherapy, etc.), or systemic use of traditional Chinese medicines or natural medicines for the purpose of treating AD within 4 weeks;
3. Systemic or topical use of PDE4 inhibitors within 4 weeks, or prior history of inadequate response or intolerance to PDE4 inhibitors;
4. Use of systemic anti-infective agents (including oral and intravenous administration), or topical corticosteroids, topical calcineurin inhibitors, topical JAK inhibitors, or topical traditional Chinese medicines or natural medicines for the purpose of treating AD, or other topical therapies for AD \[e.g., zinc oxide oil (paste), Heidouliuyou Ruangao, doxepin cream, etc.\] within 2 weeks;
5. Use of sedating antihistamines or other over-the-counter drugs containing sedating antihistamines, or topical products containing urea within 1 week prior to randomization;
6. Use of non-sedating antihistamines at non-stable doses within 2 weeks or 5 half-lives (whichever is longer) prior to randomization;
7. Use of topical antimicrobial agents within 1 week;
* Presence of severe central nervous system, cardiovascular, respiratory, hepatic, renal, gastrointestinal, urogenital, endocrine, or hematological disorders that, in the investigator's judgment, may confound study results or affect participant safety;
* Diagnosis of severe psychiatric disorders or other conditions affecting study compliance that may interfere with the conduct of the clinical study;
* History of malignancy (except for adequately treated cutaneous basal cell carcinoma, squamous cell carcinoma of the skin, and cervical carcinoma in situ, with documented cure);
* Prior severe hypersensitivity to topical dermatological preparations (including angioedema, anaphylaxis, etc.), or known allergy to any excipient of Hemay5394;
* History of long-term drug abuse or chronic alcohol abuse within 6 months prior to screening;
* Female participants who are suspected of being pregnant, are currently pregnant, are breastfeeding, or plan to become pregnant during the study;
* Participants who are scheduled to undergo inpatient surgery or require surgical intervention during the participation in the study;
* Participation in another drug/device clinical study and use of the trial drug/device within 3 months or 5 half-lives (whichever is longer) prior to randomization;
* Any other conditions that, in the investigator's judgment, make the participant unsuitable for participation in the trial.
