Composite material plate usually is anisotropic plate, To solve the bending problem for plate, trigonometric series solution in complex number form and double sine series solution are used to establish a general solution of differential equation for anisotropic thin plates in bending problem. It can be used to solve bending problem for arbitrary loading with whatever boundaries. As an example a square plate with four edges fixed has been calculated. The result agrees with that in literature. This common analytical method is simple and complete, and easy to use in practice.