The pseudo-spectral method can transform the continuous Optimal Control Problem (OCP) into a discrete Nonlinear Programming(NLP)Problem, and the solution of the original OCP is obtained by interpolation on discrete solution of NLP, which is a continuous function of the state and control.Firstly, the basic theory and general process of solving the OCP with the pseudo-spectral method are analysed.The consistency principle of the pseudo-spectral method is concluded, including the existence, feasibility and optimality.Then, methods are derived to ensure the consistency of the solution, and the applicability of the consistency principle and the method is verified through three case simulations.Finally, the characteristics of pseudo-spectral method are summarized, and general solution strategies of different scenarios and new research challenges are proposed.