Aiming at the rotary speed control of brush DC motor, design the DSP rotary speed controller. Based on DSP chip TMS320F28335, taking traditional PI control algorithm as core, introduce hardware circuit and control structure of rotary speed controller. Compare ECAP capture module with AD sampling module through clutch joint performance test. The design of speed controller is optimized and improved from an engineering perspective. The results show that the method can optimize design of DSP rotary speed controller and the signal collection accuracy is much higher than AD sampling module.