Objective To investigate the effects of overweight and obesity on the gait of primary school children by comparing the kinematic parameters between overweight/obese children and normal weight children during level walking. Methods Forty overweight/obese children (age: (9.6±1.72) year; height: (142.16±12.19) cm; BMI: (24.32±2.96) kg/m2) and 50 normal weight healthy children (age: (10.26±0.72) year; height: (139.0±7.50) cm; BMI: (17.08±1.25) kg/m2) were recruited as the subjects. All of the subjects completed 3 walking trials at preferred speed along a 10 m walkway with barefoot. A digital video camera was used to record these subjects’ level walking images, and their gait parameters, such as step length, stride length and joint angle of the lower extremity, were obtained through Shixun motion analysis system. SPSS 16.0 was used for data analysis. A paired t-test was used to assess differences of all the variables between lefe side and right side for the subjects. An independent t-test was used to assess differences of all the variables between the overweight/obese and normal weight children. Statistical significance was defined as P<0.05. Results (1) There were significant differences between overweight/obese children ((0.44±0.001)) and normal weight children ((0.45±0.001)) for relative step length (P<0.05). (2) There were significant differences in left hip and knee joint angle in the frontal plane between overweight/obese children (left hip angle: (165.36±5.29)°, left knee angle: (178.82±5.51)°, right knee angle: (177.84±5.25)°) and normal weight children (left hip angle: (161.99±4.28)°, left knee angle: (174.67±4.91)°, right knee angle: (174.67±4.91)°) during heel strike phase (P<0.05). Significant differences were found in the left ankle joint angle of the frontal plane during toe off phase between overweight/obese children((121.73±8.03)°) and normal weight children((118.44±6.70)°)(P<0.05). Conclusions Relative step length of overweight/obese children was significantly smaller than that of normal weight children during level walking. The left hip and knee joint angle in the frontal plane of overweight/obese children during heel strike phase were significantly larger than those of normal weight children. The left ankle joint angle in the frontal plane of overweight/obese children during toe off phase was significantly larger than that of normal weight children. These differences may affect the function of the lower extremity in overweight/obese children.