Objective Three dimensional gait analysis system was used to quantitatively evaluate the gait characteristics of patients with spastic cerebral palsy before and after surgery, to evaluate the efficacy of surgery and provide basis for the comprehensive treatment of spastic cerebral palsy. Methods 15 patients with spastic cerebral palsy to be treated by surgery were selected, and the gait collection before and after surgery was performed by using VICON 3D motion capture system combined with AMTI 3D force-measuring platform, to analyze the temporal and spatial parameters, kinematic parameters and dynamic parameters of the gait before and after surgery. Results After the operation, the left support phase time (p< 0.05), the right support phase time (p<0.01), the left step length (p <0.05), the step height (p < 0.05), and the maximum deviation of the COG increased (p<0.05), the step speed decreased (p< 0.01). The range of motion of the sagittal plane of the left and right hip was increased (p<0.05), the range of motion of the sagittal plane of the right and right knee was increased (p<0.01, p<0.05), the range of motion of the sagittal plane of the right and right ankle was increased (p<0.05), The range of motion on the coronal plane of the right ankle joint increased (p<0.05). When touching the ground, the Angle of left and right knee joints and the sagittal plane Angle of left and right knee joints in the gait cycle decreased (p < 0.05). The maximum plantarflexion Angle of left and right ankle joints decreased in gait cycle (p < 0.05). The maximum vertical force of left and right support was increased of gait cycle(p<0.05).