Abstract: Firstly, the non-homogeneous state equation of piezoelectric materials was derived simply from H-R (Hellinger-Reissner) mixed variational principle in this paper. And then, non-homogeneous state equation for the laminated piezoelectric plates with clamped edges was established by assuming boundary stress function. Finally the non-homogeneous state equation was transformed into the homogeneous state equation by employing the dimensional expanding method. This homogeneous equation algorithm is not only benefit to programming and the numerical stability, but also the inverse matrix calculation is avoided, thus the computing efficiency is improved greatly. Numerical example shows that the method presented in this paper is correct.