The accuracy and real-time of velocity measurement impact on the performance of the motor servo system. Incremental optical encoder measuring velocity have advantages of high accuracy and easy-to miniaturization. The typical method for velocity measurements by Incremental optical encoder is hybrid M / T method. The method is poor in real time. Raised alternate M/T method for velocity measurement. Design the software and hardware for the M/T method. The experiment results show the feasibility and correctness of the system, and the method improves the system with photoelectric encoder in real time.