Abstract: The green laser can be used for the processing of highly reflective metals such as copper. Compared with the 1 μm laser which is broadly used now, green laser has the absorption efficiency nearly an order of magnitude higher, which can better meet the needs of various fields for the precision processing of highly reflective metals. Thus, the application prospect of high power green laser is very broad. In this paper, recent progress of high power green laser based on frequency doubling technology for fiber laser is investigated in detail. The power of green laser has increased from 100 W to 1 kW, the beam quality is close to the diffraction limit, and the output power is expected to be further improved. There are two technical routes to obtain high power green laser by using fiber laser frequency doubling technology. One is to use high power single beam fiber laser as the fundamental frequency light source and cascade single-pass frequency doubling technology. The other is to use multiple-beam fiber lasers as the fundamental frequency light source, realize beam combining and frequency doubling respectively, or beam combining and frequency doubling at the same time. The former route is simpler than the latter, but the latter has the potential of higher output power. The weak absorption of frequency doubling crystal is the common problem faced by the two technical routes.