The laser diode (LD) pumped MOPA system with high frequency, large energy, high beam quality is presented. The main techniques in the LD pumped MOPA system are researched systematically. Combined computer simulation and practical application, the LD uniformly side pumped laser structure is designed, and the performance of the laser is estimated theoretically. The measures to compensate the thermal induced birefringence effect, maintain high beam quality, avoid spontaneous irradiation and improve the damage threshold are taken in the amplification process. While the repetition is 100 Hz, the single pulse energy output reaches 5 J, the pulse width is about 20 ns and the beam quality is 5 times of the diffraction limit.