Spectral combining technologies of fiber laser can overcome the limitation of the output power limit of a single-fiber laser, which is an effective technical means to obtain laser output with high power and perfect beam quality. The basic combining principles and research progress of the four spectral combining technologies are introduced. The structure, limiting factors, and characteristics of various synthetic components are analyzed separately. The key technologies of spectral combining based on dichromatic mirrors and their domestic and foreign research progress are introduced. The development prospects of spectral combining technologies are introduced.