A high-power phosphate Nd: glass laser system with 100J energy was developed. In the laser design process, the optimization of the optical layout was considered and the amplification gain of laser media was simulated. In the laser system, image relaying and stimulated Brillouin scattering (SBS) are employed to improve the quality of the output beam. A single-longitudinal mode laser pulse provided by a Nd:YLF front-end was amplified by two dual pass amplifiers and a booster amplifier, and the output energy of 106 J was obtained. In view of the requirements of SBS phase conjugating mirror employed to the high energy and high power laser system with large diameter, a new design of the SBS phase conjugating mirror was described. It is fully applicable to the high energy and high power dual pass amplification laser system.