In summary, a pulsed ultra-violet laser at 289.9 nm with good beam-quality has been investigated. And based on the nonlinear conversion of type-I phase-matched LBO and BBO crystals for extra-cavity SHG and FHG, a 289.9 nm UV laser is achieved. The average output power is 108 mW with a repetition rate of 10 kHz and a pulse duration of 8.0 ns at a total pump power of 20 W.