Dynamic optical is a theory which we can deduce the object-image conjugated rations of optical system by researching motion group in optical system. It can unify various formula and methods of optical system which have motion group. Zoom system is a typical dynamic optical system. This paper will discuss how to apply the dynamic optical theory to zoom system design. With dynamic optical theory, we can derive the image motion compensating formula and the trace curve of the image motion compensating group. The cam can be fabricated according to compensating curve, which can ensure the stabilization of image plane and keep imaging quality. Moreover, a example of 30× zoom system is presented, which proves that the dynamic optical theory has some practicability for zoom system design.