Abstract: In this paper, the mechanics character of the volume control tank was studied. The ANSYS, a finite element code, was used to simulate the mechanics characters of the volume control tank under many kinds of forces. In terms of RCC-M2000 and ASME codes, its anti-earthquake characters were evaluated. At the same time, the skirt-seat buckling was studied. The result shows that the design of the volume control tank is satisfied with the correlative criterions.