This thesis have two main objectives, namely: 1- The first objective is to study the mathematical background of the differential quadrature method and its application to solve boundary value problems of the fourth order ordinary differential equations. 2- The second objective is first about function approximation by G-spline interpolation method. Secondly the numerical solution of two applications relating the vibration of a uniform beam problem which are represented by a boundary value problem of the fourth order ordinary differential equation and the vibration of a square thin plate given by a boundary value problem of the forth order partial differential equation, by using G-spline based differential quadrature method have been obtained.