Phase-locked coherent laser array beam combination using conjugate Dammann grating and phase compensation is used to achieve high power and high brightness coherent beam combination. Theoretical analysis of the beam combination of 5×5 and 32×32 two-dimensional laser arrays using conjugate Dammann grating is carried out through numerical simulation, and the influences of the errors in the phase values of the phase plate, the matching and positioning of the conjugate Dammann grating to the beam combination efficiency during the experiment are also studied. The results of theoretical analysis and numerical simulation show that this is an efficient beam combination technique, however, these errors have a great influence on the total beam combination efficiency. This means that the manufacturing of the phase plate and positioning of the conjugate Dammann grating should be taken great care of during the experiment and the development of high power laser system based on conjugate Dammann grating, which will benefit the development of the compact, light, high efficiency and high beam quality high-power laser system.