A single longitudinal mode 320 nm UV laser with high output power is introduced in this paper.The pump source,a 20 W 444 nm InGaN laser diode,is utilized for end pumping a 15mm long Pr 3[KG-*5]+:LiYF4 crystal.And a Brewster cut LBO crystal is used inside the ring cavity for frequency doubling.The single longitudinal mode UV laser is employed as the intracavity frequency doubling crystal,while a ring resonator technique is adopted for single longitudinal mode selection.After optimizing the mirror parameters,when an incident pump power of 18 W is applied,the maximum output power of the 320 nm UV single longitudinal mode laser reaches 1.17 W,representing the highest known output power for a 320 nm single frequency laser.And the linewidth is less than 5.53 MHz.This study demonstrates the advantages of ring cavity technology in high performance UV laser production and provides new technical pathways and performance references for related fields.