The generation of ultraviolet (UV) light at 335.5 nm based on frequency quadrupling of a diode-end-pumped Q-switched Nd:YVO4 laser at 1342 nm was demonstrated. KTP crystal was used for generation of wavelength of 671 nm by intracavity doubling and LBO (BBO) crystal was exploited for the subsequent external fourth harmonic generation (FHG). With 6.3-W absorbed pump power and 10-kHz frequency repetition rate, the UV output power of 35 and 63 mW were obtained by using LBO and BBO as frequency quadrupling nonlinear crystals, respectively. The experimental results show that the conversion efficiency (red-UV) of 6.4% for BBO crystal is higher than that of 3.5% for LBO crystal, but the UV beam quality obtained by LBO crystal is better than by BBO crystal.