Rapid lunar exact-landing trajectory optimization was studied by combining a new optimal control method-Gauss Pseudospectral Method (GPM) with the traditional direct shooting method. Landing dynamics equation in high precision model was educed. Aiming at the characters of optimization method and the difficulties in optimization of lunar soft landing trajectory with many constraints, a serial optimization strategy was proposed. Firstly, control variables and state variables were dispersed, and control variables and flying time were used as optimal variables. By giving fewer Gauss nodes, initial values were obtained using GPM, and a serial optimization framework was adopted to obtain the optimal solution from a feasible solution. Then the control variables were dispersed at Gauss nodes, the precise optimal solution was obtained by direct shooting method. Simulation results show that the methodology and strategy for the optimal trajectory design have good robustness and strong convergence.