With the rapid development of computer graphics and the animation industry, character animations has been widely used in many fields such as special effects, game manufacture, multimedia education and war game. Since motion is difficult to create from scratch using traditional methods, changing the existing motions is a popular way to obtain the goal motion and create an animation library. This paper presents a method for solving the motion retargeting problem, which allows us to convert movements between characters with heterogeneous topologies. Results show that physically realistic animation can be created by using our method, and these animation retains the properties of the source animation at the most.