Abstract: Objective To analyze correlations between body mass index (BMI) and body diathesis indicators among medical students.Methods According to the requirements in "National Criteria for Physical Health of Chinese Students",height,weight,vital capacity,50-meter running,standing long jump,sit-and-reach test,sit-ups,pull-ups,and visual acuity were measured among 3 997 medical students in a medical college between March and June 2015.Correlations between BMI and these indicators were analyzed with Pearson method.Results Among the students,the mean BMI was 21.79 ±1.84 kg/m² and 87.57% of the BMI values were within the normal range; the proportion of overweight was 10.84%.Compared to those of overweight and obese students of same gender,the male students with normal BMI showed significantly higher vital capacity weight index (61.4±12.73 mL/kg),standing long jump distance (2.27±0.22 m),sit-and-reach distance (11.24±7.04 cm),and number of pull-ups (6.36±4.16 times)(P<0.05 for all); the female students with normal BMI had significantly higher vital capacity weight index (53.08+14.1mL/kg,P<0.05),standing long jump distance (1.68±0.17 m)and sit-and-reach distance (13.12±6.76 cm)(both P<0.01 in comparison with those of low weight or overweight).Better mean visual acuities were observed among the male students (4.68±0.25 and 4.68±0.27 for left and right eye)and the female students (4.68±0.24 and 4.67±0.27 for left and right eye) with normal BMI than among the students with low weight or overweight (P<0.01 for all).BMI was positively correlated with 50-meter running time in the female students (r=0.049,P<0.01)and reversely correlated with standing long jump distance,sit-and-reach distance,number of pull-ups,number of sit-ups,and visual acuity in both male and female students (P<0.05 for all).Conclusion High BMI values may be associated with poor physical health among medical students.