Abstract: In a world of increasing lightweight design demand, the selection of driving motor influences the size and quality of the overall system directly. The traditional motor selection method can meet our needs in a certain extent, however, there are also many problems that the load analysis is not comprehensive enough and the quantification degree of some influence factors is not deep enough. Therefore, the study on the motor selection method is of great significance for the lightweight design of servo system. This paper analyzed and quantified the load of opto-electronic servo system. For the loads hard to calculate accurately, a method to estimate them was provided. The dynamic characteristics of the motor was checked and the concept of confidence was introduced to help the motor selection.Furthermore, a software for motor selection was designed with Matlab/GUI and used to choose the motor of some opto-electronic pod. And a direct current motor with the confidence of 0.79 was finally chosen.