A laser-diode pumped all-solid-state 355 nm continuous-wave ultraviolet laser with intra-cavity tripling and efficient output was achieved by cavity design optimization. Ultraviolet laser at 355 nm is obtained by using a doubly cavity, and type-Ⅰ critical phase matching BIBO crystal for intra-cavity sum frequency mixing. With incident pump power of 20 W in Nd:YAG and 8 W in Nd:YVO4, TEM00 mode ultraviolet laser at 355 nm of 114 mW is obtained at last, corresponding to an optical-to-optical efficiency of 0.4%, and the power stability in 4 h is better than ±3.2%.