A high-repetition-rate,266 nm picosecond ultraviolet(UV) laser output based on β-BaB2O4(BBO) is reported.The source based on fourth harmonic generation(FHG) of a 1064 nm compact Yb-fiber laser.Using a two-crystal spatial walk-off compensation scheme,average output power of 2.9 W is gotten when pulse repetition rate is 80 MHz,and FHG efficiency of 35% from the green to UV is obtained.The dynamic color center formation due to two-photon absorption in BBO is investigated by the change of light intensity at 266 nm,and the rule of two-photon absorption coefficients and the color center densities with crystal temperature change is obtained.The experimental results show that the two-photon absorption coefficient in BBO at 266 nm is 3.5 times lower at 200 ℃ compared to that at room temperature,which improves the output power and stability of ultraviolet laser at 266 nm.