Deflection of simply supported laminated composite plate under transverse load is found out by semi-analytical method (Classical Lamination Theory) and the results are compared with Finite element method using FEA software ANSYS. The equations developed by classical lamination theory for symmetric angle ply and cross ply laminated plate are solved by Navier and Rayleigh-Ritz method. The efficiency of Navier and Rayleigh-Ritz method in solving the problems of symmetric angle ply and cross ply laminated plate are investigated by comparing their results with ANSYS. Percentage error of the results from finite element method with Navier and Rayleigh-Ritz methods are studied and compared. The model is extended to study the effect of orientation angle, number of lamina and length to thickness ratio on the deflection of simply supported composite plates for symmetric angle ply plates of stacking sequence (orientation angle) of [+