We have demonstrated a diode-pumped Q-switched Nd:YVO4 laser that pro duced ultraviolet output at 266nm by using BBO single pass fourth harmonic gener ation.When the incident pumping power was 7.9W,we obtained 63mW output and IR-UV energy conversion as great as 11% at 12.5kHz repetition rate with per pulse ene rgy of 5μJ and peak power of 252W.