Abstract: The laser peening technology is a recently-developed surface treatment method. Using an oscillation eight-stage amplified system structure and the modular design method, a short pulse and high power Nd:YAG laser system for laser peening has been developed and tested. At ambient temperature which changes less than 2 ℃, after 20 min of warm-up, the maximum pulse energy is 25 J, the energy instability is less than 3%, the pulse width is adjustable between 16 ns and 20 ns, the pulse width instability is less than 1 ns, the beam divergence is less than 2.5 mrad, and the maximum frequency is 5 Hz. A TC4 titanium alloy work-piece is processed with the laser system, the compressive residual stress is greatly improved. The results show that the performance of the laser system is very excellent.