Inclusion Criteria:
* Healthy volunteers, aged 18-55 years old (including boundary values);
* Female volunteers weighing ≥45.0 kg and male volunteers weighing ≥50.0 kg, with a body mass index (BMI) between 19.0 and 28.0 kg/m2 (including boundary values) (BMI=weight kg/height m2);
* Primary residence at an altitude of \<500 meters above sea level;
* Not ascending to an altitude \>2500 meters in the 6 months prior to the screening period;
* Voluntary participation with written informed consent.
Exclusion Criteria:
* Subjects with previous severe high altitude sickness such as high altitude heart disease, high altitude pulmonary edema, high altitude cerebral edema, and high altitude erythrocytosis;
* Subjects with established cardiovascular or cerebrovascular disease or uncontrolled hypertension (systolic blood pressure ≥ 140mmHg and/or diastolic blood pressure ≥ 90mmHg at screening);
* Subjects with clinically significant respiratory disease, digestive disease, liver disease, central nervous system disease, psychiatric disease, metabolic disease, renal disease, anemia, or acute infection;
* Subjects with primary headache (migraine, tension headache, cluster headache, etc.) or secondary headache (headache associated with infection, cerebrovascular, etc.) within 1 month prior to screening;
* Subjects with insomnia, anxiety, depression or a history of motion sickness or airplane sickness;
* Subjects with Lake Louise Score ≥ 2 at screening;
* Subjects with left index finger oxygen saturation \<95% at screening;
* Subjects with alanine aminotransferase or aspartate aminotransferase \> 2 times the upper limit of the normal range, or creatinine \> upper limit of the normal range at screening;
* Subjects with hypersensitive C-reactive protein \> upper limit of normal range at screening;
* Subjects with history of surgery or blood donation within 3 months prior to screening;
* Subjects with any medication or non-pharmacological intervention (including dietary supplements) to prevent or treat acute mountain sickness within 14 days prior to screening;
* Smoking ≥20 cigarettes per day within 3 months prior to screening;
* Contraindications to the use of Suxiao Jiuxin Pill, such as allergies;
* Women who are pregnant, breastfeeding, or have a positive pregnancy test (human chorionic gonadotropin test);
* Alcohol abuse \[more than 28 standard units of alcohol per week (1 standard unit contains 14 g of alcohol, e.g., 360 mL of beer, 45 mL spirit with 40% alcohol by volume, or 150 mL of wine)\] or substance abuse within 6 months prior to screening;
* Participation in another interventional clinical study within 3 months prior to screening;
* Other conditions, in the opinion of the investigators, make participation in this study inappropriate.
