For cylinder-embedded piston in Twin-rotor piston engine, the piston and rod are both the important component of power transmission, and their design directly affects the efficiency of engine. For comparison of the piston, ether from sealing and lubrication or the appearance, it is consistent with that of traditional engine, but the rod is different from the old one. In this paper, the static strength of rod is modeled and analyzed, and based on that the structure of rod is optimized by ANSYS workbench. It can be concluded that: for the rod, the maximum of mass, stress and deformation are determined by the three parameters, which are rod length L, width b and height H. The mass of rod is proportional to them, and the levels of impact of the parameters to the targets, from maximum to minimum, are b, H and L successively. However, a comprehensive consideration is necessary for the parameters selected based on the practical condition.