Water-jet guided laser machining technology has the advantages of low thermal effect,high precision and no tool damage,and has been applied to the machining of high-precision components. In order to reduce the diameter of laser focusing spot to facilitate the accurate coupling between laser and water-jet and improve the quality of laser hole,a method of reducing the diameter of laser focusing spot based on the principle of double-slit interference is proposed.The geometric and mathematical models of traditional water-jet guided laser and double-slit interference water-jet guided laser drilling are constructed. Based on COMSOL simulation,the effects of traditional and double-slit interference water-jet guided laser drilling on the evolution of laser hole profile,the distribution of heat affected area and the size of recast layer are compared and analyzed under the same laser beam parameters and processing conditions.The results show that compared with traditional water-jet guided laser,the double-slit water-jet guided laser processing technology can effectively reduce the diameter of laser hole,the cone angle,the width of heat-affected area and the size of recasting layer,and further reduce the diameter of laser focusing spot under the existing conditions.