thesis, we present an extension and also modification for the Gauss pseudospectral method using the hybrid of block-pulse functions and Lagrange polynomials based on the Legendre-Gauss points. In this respect, we derive the corresponding operational matrix of derivative according to the weak representation of the derivative operator. In order to demonstrate the applicability and efficiency of the method, we examine three nonlinear optimal control problems and two nonlinear delay optimal control problems.