The technology on spectral beam combining of fiber lasers to achieve high power laser output and high beam quality is reviewed and illustrated. Two ways of spectral beam combing including volume Bragg grating combining and multilayer dielectric grating combining are introduced. The principle of spectral beam combining,high power narrow bandwidth fiber lasers,grating components and the schemes of beam combining are analyzed. Furthermore,the developments of spectral beam combining of fiber lasers at home and abroad are summarized as well.