This paper describes the study on the SCARA robot motion. The accurate motion control of the robot becomes more important as it is introduced to various kinds of works, especially the robot is used in continuous path control mode. But there are many kinds of factors lying down in the robot motion. They are very complicated, and it is not so easy to find out the factors of robot motion error. In this report, the method applying the experimental measurement and the numerical simulation jointly, is taken to find out the factors. In conclusion of the application, it is pointed out that the main factor of the SCARA robot motion error is the delay of two motors controlled by servo system. The positional error of the tool point path is mainly caused by the delay unbalance of two motors which actuate the first and the second arms.