Abstract: Coherent combination of multiple segmented beams is one of the critical technical issues of high-power solid state lasers. Coherent beam combination by four group tilt/tip-piston mirrors is simulated by the stochastic parallel gradient descent (SPGD) algorithm. Locking phases is performed by running the SPGD algorithm on a coherent beam combination model. The results show that the far-field intensity ratio of four coherent beam combination within the 20-μm-diameter spot is nearly four times higher than that of incoherent beam combination in finite iterations. Simulation results validate that coherent beam combination could be realized with high-frequency response actuators and corresponding high-speed control algorithm.