Stochastic parallel gradient descent (SPGD) is an effective way to achieve multi-channel phase-locked laser beams for coherent beam combination (CBC). In this paper, the influence of piston error and tilt error on CBC is primarily presented. Then, an arrangement model of 2×2 laser beams is built. With this proposed model, SPGD is tested and verified. Key parameters, the gain coefficient and the disturbance amplitude, impacts on the error control performance of the algorithm, are analyzed and optimized. The surveys show that it is necessary to control piston error and tilt error for CBC. When SPGD is used to correct the above errors, the convergence speed of the algorithm is improved with the increase of the gain coefficient and the disturbance amplitude, however, the accuracy of SPGD is reduced and the system is vibrated. In order to improve CBC, the adaptive gain coefficient is studied. Compared with the fixed gain coefficient, the adaptive gain coefficient is able to make a good balance between the convergence speed and the accuracy of the algorithm, which indicates that the adaptive gain coefficient is an effective optimization way. These results in this paper provide a theoretical reference for CBC using SPGD in a large short-pulse laser facility.