The study of coherent addition techniques of fiber laser is very significant to obtain the laser with high power and good beam quality simultaneously,and the coherent addition techniques of other lasers have vital suggestive action on them. The basic principle and development of coherent addition techniques of laser beam are introduced. The various coherent addition methods are classified according to their combining mechanism,and the mechanism and difficulty of these methods are expounded in details. Finally,the comparisons and simple comments about the methods are discussed,and the three promising coherent addition methods are indicated.