A green laser system with high average power output is developed with high energy and narrow pulse width. With diode laser pumped Nd:YAG crystal, RTP electro-optic Q-switching and power dividing by master oscillator power amplifying (MOPA), the 532 nm green laser output with high energy, narrow pulse width and high repetition rate is realized. For the fundamental frequency output at 1064 nm, the average pulse energy is 213 mJ, the operating frequency is 100 Hz and the optical-optical conversion efficiency is 12%. While a type Ⅱ phase matching high gray track resistance KTP crystal is used for extra cavity frequency doubling, an green light output at 532 nm can be obtained, with the average pulse energy of 127 mJ, the operating frequency of 100 Hz, the pulse width of 7.2 ns, the beam quality of 20 mm·mrad and the total wall plug efficiency of 2.1%.