Targeting at the horizontal tank with jacket from a certain project as the research subject, applying the finite element software ANSYS Workbench, the structural static analysis showed that under the full load and the snow condition the deformation and stress were similar and the reinforced rib had significantly effect on the tank. Meantime, the response spectrum analysis told that under the seismic condition the maximum stress occurred in the saddle, which was lower than the allowable stresses of the materials. The reliabilities of the tank were validated, and optimization method was presented.