Objective To study the body composition of public security staffs and to prevent sub-health condition positively. Methods Body compositions of 771 public security staffs were measured and analyzed with bioelectrical impedance analytic process (BIA). Results The male public security staffs had obviously lower body fat percentage (P< 0.01) but higher body mass index and obesity (P<0.05) than female public security staffs. Both male and female public security staffs fad the highest content of fat in the lower limbs. The body part ranked the second place, followed by the upper limbs. Measured by body-fat percentage(BF%), the obesity rate of the male and female staffs was 10.08% and 45.59% respectively. Measured by body mass index (BMI), the hypergravity rate of the male and female staffs was 44.09% and 20.59% respectively; and the obesity rate of the male and female staffs was 8.35% and 0.74% respectively. Measured by obesity degree (OBD), the hypergravity rate of the male and female staffs was 21.73% and 4.41% respectively; and the obesity rate of the male and female staffs was 11.65% and 1.47% respectively. Conclusion Public security staffs should pay attention to their over-weight and hyper-fat level. Proper dict and body exercise are needed.