Abstract: In order to improve coupling efficiency of laser energy of monocrystalline silicon in laser processing, a short laser pulse and a long laser pulse were used to form a combined pulse to irradiate the monocrystalline silicon. The process was simulated by using COMSOL software. The influences of the delay time of combination laser and the laser energy density of long pulse on the process effect were obtained. The effect was compared with that of individual action millisecond laser under the equal total energy. The measured damage morphologies of monocrystalline silicon irradiated by lasers with different power intensities were in agreement with the trend of numerical results. The results show that the combined laser can improve the coupling efficiency of laser. The different delay time would affect the process effect of the combined laser. The optimum delay time is 0.1ms. When the ratio of the millisecond laser energy density in the combined laser is relatively low, the effect is obvious. With the increase of the ratio of the millisecond laser energy density, the enhancement of the effect is relatively slow. The research results can provide theoretical and experimental basis for the application of combined laser.