Abstract: In order to achieve high reliability, narrow pulse width and high peak power laser output, an all-solid-state electrooptical Q-switched green laser with diode side pump was designed with the side-pumped and electrooptical Q-switched technology. The stable laser output of LD side-pumped Nd: YAG pulse green laser with extra-cavity frequency-doubled KTP was achieved by the simple and compact flat-flat cavity design. When the pump current is 120A and repetition rate is 600Hz, the highest pulse green output average power of 3.62W, the conversion efficiency (from 1064 nm to 532 nm) of 15.3%, the pulse width of 21ns, peak power of 300 kW, and single pulse energy of 6.01mJ were achieved. Experimental results show that the stability of laser output is high, pulse width is relatively narrow, and peak power is high.