Abstract: Objective To investigate the significance of hydrogen sulfide（H 2 S） and nitric oxide（NO） in high altitude hypertension. Methods One hundred twenty-seven workers received healthy check-up before entering high altitude and worked at this circumstances （5 000 m above sea level）for 1-3 months. The living condition, intensity of work and the time of recovery in plateau were similar among them. Seventy-eight suffered from high altitude hypertension （Ⅰ-Ⅲ grade） and 49 persons were in normal blood pressure. The serum content of H 2 S and NO were measured by sensitive sulphur electrode and Griess. Results As compared with normotensives, serum level of H 2 S and NO evidently increased in high altitude hypertension（34.5% vs 28.4%, P＜0.05）, high SBP altitude hypertension（36.9% and 33.1%, P＜0.05）, and high DBP altitude hypertension（31.7% and 39.7%, P＜0.05）. The content of H 2 S and NO in blood was increased with the grades of BP especially for H 2 S（R 2 =0.918）, H 2 S and NO were closely related to DBP, while they are negatively related to O 2 saturation（R 2 =0.374, P=0.001）. Conclusion The metabolism of H 2 S and NO was associated with high altitude hypertension morbidity.