The beam quality has been improved efficiently by means of a varied reflectivity mirror (VRM) unstable resonator used in a tunable Ti∶Al 2O 3 laser, and a tunable blue laser from 396 nm～440 nm through second harmonic generation (SHG) by LBO crystal is generated. The highest SHG efficiency of 27.2% and the maximum output energy of 26 mJ have been obtained.