In this paper, a virtual prototype of the shovel loader with four tracks was established, and the tension adjustor’s F-t curve under driving conditions was obtained by the simulation. Then, the finite element analysis and the dimension optimal design of the tension adjustor which is an important part of the tracked vehicles were carried out so as to find out its best bearing structure. At last, the new model after optimization was analyzed again. According to the comparison between the finite element analyze results before and after the optimization, the finite element model’s maximum strain and stress under working condition after the optimal design were greatly cut down. As a result the using safety of the tension adjustor and its service life were greatly improved.