Abstract: Approximate theory for rectangular plates with in-plane stiffness gradient subjected to transverse loading is established. In this theory, Reissner-Mindlin assumption is introduced, and the shear deformation in the mid-surface of the plate is considered. Material properties of the plates vary exponentially in the direction parallel to one pair of edges. Analytical solution in the cases that one pair of edges of the plate is simply supported and the other pair is fixed or simply supported is obtained. It is indicated that this solution can degenerate into the classical solution of thin plates based on the well-known Kirchhoff assumption if the shear deformation in the mid-surface is ignored. The numerical results of this solution are given and compared with those from 3D finite element solution by means of PATRAN code. It shows that the precision of this solution is still high even for thick plates.