Coherent beam combining (CBC), used in scaling power by phase-locking multi-lasers, is an efficient approach to achieve high brightness laser. Based on this approach, the current study analyzed the mechanism of mutual injection-locking and its influence to the laser coherence. Furthermore, two independent Nd:YAG lasers were associated with each other by polarized elements, achieving the mutual-injection-locking of two lasers. Coherent laser power reached 4.4W and the peak intensity rosed up to 1.4 factor. Thus , this research made an tentative exploration of the high power coherent beam combining laser.