Abstract: Based on the theory of mechanics, a structure model is built for wobble-plate engines. By analyzing the linkage's response to shaking force, the whole system wasdivided two parts, a multiplex open chain linkage and a circular linkagewith N pistons. Then the complete force balance of the two parts isstudied separately. The results show that the wobble-plate engine willattain a complete force balance by adding only a counterweight on theprincipal axis. The method is simpler and more convenient than that ofanalyzing single loop spatial RRSSC linkage, so it can be used for specialenvironments.