The arrangement of laser beams influences the efficiency of coherence. The article analyses how filling factor influences the efficiency of coherence based on theories calculation and simulation. In the meantime, the article analyses how the orientation error caused by each beam’s installation error influences the efficiency of coherence, and these installation errors are hard to be avoided whatever in experiments or ultimate engineering practice. According to the result of analysis, a project tentatively named off-axis focusing arrangement is proposed, theoretical model is built up, and the inside contact of focal distance, beam waist and the peak power are got. Ultimately, the article contrasts the simulation result between off-axis focusing arrangement and parallel arrangement, discusses the merits and shortcomings of each other, and provides a convincing theory support to the following experiments.