It is the purpose of this paper to design a high-performance locking-free low-order plate element, based on the Hellinger-Reissner variational principle of Mindlin-Reissner plates. By means of the energy optimization condition，we present a 7-parameter bending moment field, and assume that the equilibrium equations associating bending moments with shear forces are satisfied strictly within the elements. With the aid of a reduced interpolation operator, we obtain an accurate locking free quadrilateral hybrid element. The numerical experiments reveal that the proposed plate element possesses good properties despite distorted meshes, and is free of shear locking in the case of very thin plates.
