A laser diode-end-pumped Nd∶YVO4 intracavity frequency-tripled quasi-continuous 355 nm laser has been demonstrated. The efficient second and third-harmonic generation with the high peak power and stable operation is generated by two lithium triborate (LBO) crystals. The laser cavity is a simple plane-to-plane linear cavity with the cavity length of 108 mm. An average 355 nm laser with output power of 245 mW is obtained at a pump power of 6.76 W, a pulse repetition rate of 20 kHz and the highest optical-to-optical efficiency of 3.62%. The corresponding pulse width and pulse peak power are 8.0 ns and 1.52 kW, respectively. The instability is less than 4.2% and the beam quality is satisfactory. This technique can decrease some optical elements reduce the size and enhance the handiness of the laser. These advantages will benefit the broad applications of the ultraviolet lasers.