The invention discloses a method for preparing a microstructural target by using laser to improve a laser propulsion impulse coupling coefficient. In the method, preprocessing treatment is performed on a solid target in an ablation laser propulsion technology by a focused near-infrared femtosecond laser pulse, so that microstructures in various shapes can be generated on the surface of the solid target to effectively enhance the impulse coupling coefficient. The microstructural solid target prepared by the femtosecond laser pulse comprises a plurality of types of protruding structures and groove structures which contribute to enhancing light absorption. By a high-sensitivity torsion balance precision measurement device established by experiments, the impulse coupling coefficient of the microstructural solid target is improved by about 170 percent compared with that of a common plane target which is not preprocessed by femtosecond laser within a laser flux variation range of 0.6 to 100joules/square centimeter. The new method for effectively enhancing the conversion from light energy to mechanical energy in the laser ablation process is potentially and importantly applied in the technical field of laser propulsion.