Due to the requirement of laser conditioning system of ICF drive. A Nd: YAG laser system with high power and high beam quality is developed. Compared to current common laser system, it has an apparent improvement in temporal shape and beam quality. The system applies several technologies and teaches as following: a single longitudinal mode oscillator with a passive Q-switch; SBS pulse compressing technology; SBS pulse phase-conjugation technology; image relay technology and high efficient pumping cavity. Its main technology indexes are listed as pulse width 3ns ,energy 1.1J,far field diverge angle 0.3mrad,repitition frequency 10Hz.