The principle and progress of polarized beam coherent combination is described. The influence factors, such as beam parameters, the change of amplitude-ratio and phase-difference, beam overlap-ratio and parallelism on the combining efficiency, are researched. The experimental parameters and methods of operating combining are also discussed. The results show that the influence of phase-difference variation on combining efficiency is much greater rather than the change of amplitude-ratio, and the effect of the overlap-ratio error is so small that it can be ignored when it is smaller than 2.5%. Moreover, the parallelism error makes the combining efficiency have a significant decrease. It is found that combining beams with large beam diameter have a benefit for the effective reduction of combining loss caused by the parallelism error, the combining efficiency is greater than 95% when the beam diameter is 8 mm and interference of equal thickness is used to test the coincidence. In addition, beam combination with identical intensity is the best method for getting the maximum intensity and simplifying operation.