Abstract: In this paper, a simple formulation of hybrid/mixed finite element is established based on the principle of weighted residual approach. A quadrilateral hybrid/mixed thin plate bending element-QP12 element is constructed. Its geometrical invariability is kept by using natural coordinate interpolation functions. The matrices used in constructing its stiffness matrix are given in explicit forms without involving numerical integration Thus the inverse calculation of high order matrix is avoided and the computational efficiency and precision are increased.The numerical results show that QP12 element has higher accuracy in both stresses and displacements, and has strong adaptability in various load cases and boundary conditions.