Laser coherent synthesis is an effective technique for enhancing laser power and maintaining beam quality in fields such as remote sensing and communication. The filling factor affects laser coherent synthesis and plays a critical role in assessing coherent synthesis arrays. However, it is not a comprehensive factor. Accordingly, this study introduces plane wavefront distortion (PWD) as an integrated parameter for evaluating the performance of laser coherent synthesis. PWD simultaneously considers factors such as beam quality, array alignment, and component manufacturing errors. Based on the theoretical derivation of the expression for PWD and analysis of its effect on the efficiency of the system, simulations and experimental measurements demonstrate that PWD can be used to reflect the overall efficiency of laser coherent synthesis, exhibiting a negative correlation with it. The findings offer scientific value for the practical application of wavefront modulation techniques in coherent beam combinations in multi-aperture laser array coherent combination systems.