【Objective】 To clarify the hematological characteristics and current situation of chronic mountain sickness among Tibetan residents in extreme high altitude area (more than 5 000 m above the sea level) of Ali district based on the analysis of physical examination and blood test results. 【Methods】 Totally 250 Tibetan residents were selected by convenient sampling for blood oxygen saturation (SpO2), heart rate, and blood routine examination. Chronic mountain sickness was determined according to the hemoglobin (Hb) level and SpO2. 【Results】 The red blood cell (RBC), Hb and hematocrit (HCT) of the Tibetan residents at 5 200-meter altitude were all higher than the normal physiological reference range of China. Mean red blood cell volume (MCV), mean red blood cell hemoglobin content (MCH), mean red blood cell hemoglobin concentration (MCHC), white blood cell (WBC) and platelet (PLT) were in the upper limit of the reference value. The RBC, Hb, HCT and MCHC of male Tibetan residents were higher than those of females, while PLT was lower than that of females, with significant differences. There were no statistical differences in MCV, MCH or WBC among different genders of Tibetan residents. The SpO2 of the Tibetan residents was about 85% of the normal value, and the males had higher SpO2 than the females in the same age group, and the difference was statistically significant, but the heart rate did not differ significantly. The prevalence rate of chronic mountain sickness in this area was as high as 16.4%, and the prevalence rate of heavy manual workers was significantly higher than that of light manual workers, with significant differences. 【Conclusion】 The high-altitude anoxic environment causes the changes in red blood cells, hemoglobin, and oxygen saturation of local residents, and the prevalence of chronic mountain sickness increases significantly. Labor intensity is one of the risk factors for chronic mountain sickness in high-altitude areas.