The error kinematics mathematic model of 6-DOF robot and 2-DOF positioner was established on the basis of differential transformation matrix. When robot was machining, the dynamic error and the static error were coupling. The relationship between two adjacent rod of the dynamic error and the static error was analyzed on the perturbation method, and then the relationship of dynamic error and the static error between robot end effector and each joint was built. Based on the perturbation method, the synthesis error compensation model was created by decoupling the dynamic error and the static error， and then the effectivity of the compensation model was proved. The compensation value of each robot joint can be obtained from the model.