Abstract: For the high precision direct drive permanent magnet linear synchronous motor （PMLSM） servo system,the influences to the servo performance were analyzed,including the load disturbances,parameters changes of the system,end-effect and uncertain factors. A robust repetitive control strategy based on combining the disturbance observer （DOB） and repetitive controller （RC） was proposed. The robust feedback controller based on DOB can overcome the influences of the uncertainties,such as external disturbance,load disturbance,un-modeled dynamics and the parameters perturbation and so on. It can ensure the robust performance of the system. But the influences to velocity quality for periodic disturbance generated by specially existing end effect of PMLSM cannot be entirely restrained by DOB. For it,according to inner model theory,repetitive controller was designed to entirely eliminate the influence of the periodic disturbance. The theory analysis and simulation experiment results show that the control scheme is effective,and the robust performance is improved greatly.