To analyze the machining performance of grinding machine and improve the quality of tooth surface, this paper proposes an integrated model of processing performance evaluation of computer numerical control gear grinding machine. Based on the gear profile grinding machine kinematics principles, the topology modification formulas of tooth surface were deduced. Calculated the process capability index according to experimental data and found that the tooth surface errors were followed normal distribution. The main reason of formation errors was analyzed by cause and effect diagram. Finally, the validity of this integrated model of processing performance evaluation is numerically demonstrated using CNC gear grinding machine.