The side-coupling technology for double-clad fiber can transfer pumping light into inner cladding through the side of the fiber．It has many advantages over end-pumping technology on high power fiber lasers.There are several kinds of side-coupling technology,such as fiber angle-polished,micro-prism,V-groove,embedded mirror and diffraction grating side-coupling.The structures,theories and performance parameters of these technologies are introduced and the problems of each method are analyzed.