Abstract: The laser damage of HfO2 /SiO2 high reflector coating with and without l /2 silica overcoat was studied in detail respectively, the damage threshold and possibility was measured by using a 1064nm longitude mode, 10ns Nd: YAG laser, the laser damage size and morphology were observed and analyzed by using a Normaski microscope, main conclusions are as follows: (1) The l / 2 silica overcoat does affect laser damage threshold of HfO2 /SiO2 high reflector coating significantly，and increase the laser damage threshold of coating up to 1.5 times; (2) According to laser damage morphologies, l / 2 silica overcoat can reduced the serious damage of HfO2 /SiO2 high reflector coating, and prevent catastrophic damage of the hafnia top layer; (3) For multi-shot laser pulse, l / 2 silica overcoat can grea