Taking the variable speed pump control motor system as the research object, in order to improve motor speed antiload disturbance capability. The speed control method on variable speed pump control motor system was researched. Mathematical models for variable speed pump control motor system were established. The method on linear quadratic(LQ) was proposed based on mathematical models. The simulation and experimental study were conducted based on a company pumpmotor test platform. The results show that the control method has good control effect, can achieve stable output of motor speed. The research can lay theory and practice foundation for application of variable speed pump control motor system.