The transient thermal shock performances and relevant damage mechanism of pure W and lutecium doped W alloys were investigated via a repetitive laser beam heat load test to simulate the transient heat load events such as edge-localized-modes(ELMs)on the plasma facing materials in future nuclear fusion reactors.The test was performed with the laser beam test facility LSW-1000 at room temperature with a pulse width of 2 ms and a current of 60A,the corresponding laser energy density of which was up to 50MW/m2.The laser beam focused perpendicularly on the sample surface with a spot diameter of 1.5 mm.