With the rapid development of micro-nano satellites, the performance of micro-thrusters is required to be higher. Because of its high specific impulse, precise thrust control and low energy consumption, the laser-propelled micro-thruster provides an excellent micro-thruster choice scheme for micro-nano satellite. In this paper, the influence of power density and pulse width of semiconductor laser on the performance of laser propulsion was studied in transmission ablation mode. The results show that when the thickness of the working medium layer is 200 μm, with the increase of the laser power density, the single pulse impulse and specific impulse gradually increase. And there is an optimal power density value to the impulse coupling coefficient and ablation efficiency. As the pulse width of the laser increases, the impulse of the single pulse gradually increases, and the specific impulse first increases and then decreases. At 250 μs, the specific impulse reaches its maximum value, which is about 221.8 s. The impulse coupling coefficient and ablation efficiency decrease with the increase of pulse width. When the pulse width exceeds a certain critical value, it will have a bad effect on the target pit of the laser ablation working medium, resulting in a serious waste of laser energy and working medium. The optimizing of laser parameters provides a reference for the engineering application of laser propelled micro-thruster.