Abstract: In this paper, based on the principle of the minimum potential energy for mixed variables, the equations of the flexural surface of the rectangular plate in the elastic stage under the hydrostatic pressure are derived under three different boundary conditions: three sides simply supported and one side fixed, two adjacent sides simply supported and three sides simply supported,and by using the numerical analysis software, the obtained numerical solution and the finite element simulation values are obtained. The results show that the method adopted in this paper has good practicability for various related problems in engineering practice, and the calculation method provides a new way for solving engineering practical problems.