In order to increase light intensity on the target plane, laser beam array target shooting is usually used in high power laser driver divices, in which 2×2 beam array is widely used at present. The lenses adopted in beam array focusing system lens include off-axis lens and non-off-axis lens. The excellent quality of focal spot can be obtained under ideal conditions when we use the beam array focus system with non-off-axis wedged lenses. The optical propagation model of 2×2 beam array focus system is built, and the influences of various errors on its focal spots during the process of actual installation and adjusting are simulated and investigated. Results show that the mirror angle and the lens translation have great influence on the focal spots quality of the system, and the two components should be precisely adjusted. The influences of mounting angle and focal length error of the lens on the system focal spots quality are relatively little, and it is easy to be satisfied at the present conditions. The researcher′s understanding about multi-beam coherent combination scheme can be improved by this study, and it has a certain guiding significance for the installation and adjustment of practical systems.