In order to optimize the mechanic property of the balanced tworing axial piston pump's cylinder, the force situation of the cylinder is analyzed, and the mechanical model and simulation model are established. Finite element analysis (FEA) on the cylinder was studied, and the cylinder’s response curves of the stresses and strains were obtained on the different structure parameters, so the cylinder's structure could be optimized. The stress-strain diagrams on the different load were analyzed. The results show that the balanced tworing axial piston pump has good mechanic property. The cylinder's maximum axial strain and maximum radial strain depend mainly on deformation of the outside ring. Compared to the cylinder of only inside ring and only outside ring, the two-ring cylinder's axial strain and radical strain is much less than the sum of only outside ring and only inside ring, and it indicates that the force of the two-ring cylinder can be offset, so the two-ring cylinder's structure has certain advantages.