Objective To analyze gait characteristics of patients with spastic cerebral palsy (CP) before and after functional selective posterior rhizotomy (FSPR) surgery, so as to evaluate curative effects of the surgery objective ly. MethodsFifteen patients with spastic CP to be treated by FSPR were selected. The VICON three-dimensional (3D) motion analysis system and AMTI 3D force plates were used to collect and analyze the spatiotemporal gait parameters, kinematic and dynamic parameters before and after FSPR surgery. Results After the surgery, the left and right support phases were longer,and the left-side step length was significantly larger. The step height, velocity and the max displacement of center of gravity (COG) in coronal plane were smaller than those before surgery.The sagittal plane angle (flexion and extension angle) of the knee during initial landing was significantly increased, while no significant differences were found in that of the hip and ankle.The range of motion (ROM) of the left/right hip, knee and ankle in sagittal plane was increased to some extent during walking, with statistical differences. The ROM of right ankle in coronal plane was also increased obviously. The minimum flexion angle of the right knee and the maximum plantar flexion angle of the left/right ankle were significantly reduced. The maximum vertical forces of left and right support phases were significantly increased, while no significant differences were found in torque of lower limbs. Conclusions The 3D gait analysis can be used to evaluate the effect of FSPR on patients with spastic CP. The spasticity of patients with spastic CP is relieved after FSPR surgery, and the spatiotemporal gait parameters and kinematics parameters are improved significantly. But the improvement of dynamic parameters was not obvious, and further rehabilitation treatment is needed.