We reported a high energy, high beam quality LD side-pumped narrow nanosecond pulses Nd∶YAG_{laser amplifier. The amplification system consists of a nanosecond electro-optic Q-switched oscillator and a two-stage side-pumped Nd∶YAG rod amplifier. The oscillation stage uses Nd∶YVO4 crystal as the gain medium to reduce thermally induced birefringence and reduce intra-cavity losses. The amplification stage adopts a two-stage amplification structure to improve the magnification. Finally, when the pulse repetition frequency is 10 Hz, 1064 nm laser output with maximum single pulse energy of 377 mJ, pulse width of 5.9 ns, and average beam quality factor of 1.86 is obtained.}