Abstract: The coolant liquid lead-bismuth eutectic alloy (LBE) of the accelerator driven subcritical reactor system (ADS) would lead to serious cavitation erosion on the main pump impeller and the first wall cladding material when the liquid LBE flows at a high speed. Welding joint is the weak area in the whole circulation pipeline, and the reasonable heat treatment is the most effective method to improve the performance of the weld area. A suit of ultrasonic cavitation facility was self-designed to the cavitation erosion test. By analyzing the surface topography, roughness and mean pit depth of specimens after being eroded for different time, and combining these erosion results with the microstructure and mechanical properties of weld bead after PWHT, the cavitation behavior of weld bead of CLAM steel after PWHT and the influence of PWHT to the cavitation behavior of weld bead were studied. The results show that the weld bead being quenched and tempered showed the best cavitation erosion resistance. The cavitation erosion resistance of weld bead after being tempered at 760℃ were better than that of weld bead after being tempered at 710℃ or 810℃. The weld bead without PWHT exhibited the poorest cavitation erosion resistance.