Objective: To understand the cardiopulmonary endurance status of Tibetan middle school students in different high altitude areas and the relationship with body mass index (BMI), and to provide reference for cardiopulmonary endurance improvement among students in different high altitude areas. Methods: From October to November 2019, 3 819 Tibetan middle school students in Linzhi, Lhasa, and Nagqu Regions of Tibet were tested with the 1 000meter run for boys and 800 meter run for girls, and BMI was calculated. The cardiorespiratory endurance of middle school students in different high altitude areas was compared, the detection rate of wasting, normal, overweight and obesity was compared with the χ 2 test, and the relationship between body mass index and cardiorespiratory endurance was analyzed by multiple linear stepwise regression. Results: The differences in VO 2max between Tibetan middle school students aged 13-15 and 17-18 years in Nyingchi, Lhasa and Nagqu were statistically significant( F=26.72, 13.75, 23.86, 8.68, 9.35, P <0.01), and 13-14, 16-18 years old girls in three regions with VO 2max ( F=5.29, 4.36, 11.38 , 7.79, 16.30，P <0.01). The proportion of boys wasting in Linzhi area was 10.2%, that of Lhasa area was 8.7%, and that of Nagqu area was 17.5%, the difference was statistically significant( χ 2=25.91, P <0.01); the proportion of girls wasting, Linzhi, Lhasa, and Nagqu were 2.6%, 2.5%, 5.1%, the difference was also statistically significant( χ 2= 8.35 , P <0.05). Multiple linear stepwise regression analysis showed that after body mass index and altitude included, the model △ R 2=0.075, and Tibetan middle school students were overweight and obese ( B=0.44, 95%CI =0.39-0.49) and positively correlated with VO 2max ( P <0.01); weight loss ( B=-0.36, 95%CI =-0.42--0.29) was negatively correlated with VO 2max ( P <0.01); altitude [Lhasa Area： B(95% CI )= -0.44(-0.49--0.39)，Nagqu Region： B(95%CI )=-0.51(-0.56--0.45)] was negatively correlated with VO 2max ( P <0.01). Conclusion Overweight and obesity are positively correlated with VO 2max , and weight loss and altitude are negatively correlated with VO 2max . The proportion of wasting among Tibetan middle school students in high altitude areas needs to be focused for cardiorespiratory endurance improvement.