Abstract: In view of problem that parameters of DC motor such as armature impedance and rotor rotating momentum may change with operating environment and working conditions of the motor, resulting in control failure of the system, an on-line identification method of time-variable parameter of DC motor based on recursive least squares algorithm was given, and control system of DC motor with TMS320F2812 as the core was designed. The experiment results show that the system with the recursive least squares algorithm can achieve effective identification of time-variable parameter of DC motor system.