Key Inclusion Criteria:
1. Aged 40 to 80 years (inclusive) at the time of screening visit (Visit 1), male or female;
2. Subjects diagnosed with chronic obstructive pulmonary disease (COPD) in accordance with the GOLD 2026 diagnostic criteria prior to screening \[GOLD 2026 criteria: presence of chronic respiratory symptoms such as dyspnea, chronic cough or sputum production, and/or a history of risk factor exposure, and the pulmonary function test results show: the forced expiratory volume in one second (FEV1) after using bronchodilators / forced vital capacity (FVC) \<0.7\];
3. At screening visit (Visit 1):
* Post-bronchodilator FEV1/FVC \< 0.7; and
* Post-bronchodilator FEV1 ≥ 30% and \< 80% of predicted value;
4. Modified Medical Research Council (mMRC) dyspnea scale score ≥ 2 at screening;
Key Exclusion Criteria:
1. Known hypersensitivity to HSK39004 inhalation suspension, salbutamol, or any component of the drug delivery system;
2. History of life-threatening acute exacerbation of COPD;
3. Acute exacerbation of COPD (excluding the use of short-acting bronchodilators alone) or hospitalization for pneumonia within 12 weeks prior to screening (Visit 1);
4. Acute (viral or bacterial) upper or lower respiratory tract infection within 6 weeks prior to screening (Visit 1);
5. Diagnosis of any other clinically significant respiratory disease besides COPD, including but not limited to: alpha-1 antitrypsin deficiency, bronchial asthma, active tuberculosis, lung cancer, pulmonary edema, cystic fibrosis, bronchiolitis obliterans, pulmonary sarcoidosis, or clinically significant idiopathic pulmonary fibrosis, pulmonary arterial hypertension, bronchiectasis (except asymptomatic localized bronchiectasis) that, in the opinion of the investigator, poses a safety risk to the participant or may affect the analysis of study result;
6. Severe or uncontrolled cardiovascular disease or history;
7. History of malignancy (except for carcinoma in situ, cutaneous squamous cell carcinoma, and basal cell carcinoma cured for more than 5 years), suspected malignancy, or undetermined neoplasm;
8. Concurrent severe, uncontrolled renal, neurological, endocrine, thyroid, urological, ophthalmic, immunological, psychiatric, gastrointestinal, hepatic, or hematological diseases/abnormalities that, in the investigator's judgment, may pose a safety risk to the subject or confound study outcome analysis;
9. History of lung lobectomy or lung volume reduction surgery within 12 months prior to screening;
10. Subjects determined by the investigator to require oxygen therapy;
11. Clinically significant sleep apnea requiring continuous positive airway pressure (CPAP) or non-invasive positive pressure ventilation (NIPPV)
