According to the optimization principle for diodepumped laser, one kind of mini diode-pumped laser for seed-injection is designed. Using the numerical method, the optimized design is presented laser gain media, coupling system and resonant cavity. The seed laser beam from mini diodepumped laser was injected into Q-switched laser and output characteristics of Q-switched laser were studied. The experiment results show that this laser is stable, with high beam quality and small light beam divergence. The lightlight efficiency is 17.4% and slope efficiency is 24%. The output power of this laser is about 80mW. The buildup time of laser pulse in power oscillator decreases by 40ns and the injectedseed laser field improve the distribution of output laser field.