Constrained by such factors as thermal damages and nonlinear effects, the single-mode output power of one single fiber lasers is limited. Spectral beam combining technology to integrate different laser outputs based on some means is believed to be an inevitable choice to achieve high power laser output. The development process and current status of spectral beam combing technology are introduced and the basic principle, key factors, advantages and disadvantages of several common kinds of spectral beam combing systems are presented. The latest progresses on narrow linewidth high power fiber laser and its spectral beam combining in Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, are also introduced, and the development prospects of spectral beam combining technology of high power fiber lasers are prospected.