The infrared (λ0=830nm)nanosecond pulse is generated by pumping Ti:s apphire with diode-Q-YLF laser, and then the second-harmonic blue laser (λ 0=415nm)is obtained by frequency-doubling with the crystal Li BO20(LBO). In our experiments, the fundamental wave with a power of 960mW and cor responding harmonization of 285mW are output from the laser system when pumping power is only 3W. The high fundamental conversion efficiency of 32% and the seco nd harmonic conversion efficiency of 322% are reached, by optimizing the desig n of Ti:sapphire laser system and the focusing system in frequency-doubling. The influences of the bandwidth, the polarization and the focusing of the fundament al wave on the second-harmonic generation are discussed.