Because of the relatively soft interlaminar shear modulus in high performance composite, the laminated plate theory based on the kirchhoff hypothesis becomes inaccurate for determining gross plate response of thick composites and a thick angle-ply, fiber-reinforced plastic(FRP) faced sandwich plate type with thick core. In this paper a procedure is developed for accurately calculating the mechanical behavior of sandwich plate type with thick core of arbitrary stacking sequences. The procedure is an extension of an existing laminate plate theory which includes the effect of transverse shear deformation and is easily computerized for design application with a minimum running time. The accuracy of the approach is ascertained by comparing solutions from the sandwich plate theory to the composite laminated plates theory including the effect of transverse shear deformations. Comparison study has also been made on laminated plates according to a First-order shear deformation theory(FSDT), Higher-order shear deformation theory(HSDT) and Classical plate theory(CPT).