Laser micro-propulsion is a new laser-powered electric propulsion technology, which uses the mechanical effect generated by laser-matter interaction. Liquid as propellant is the latest points of interest. Impulse coupling characteristics of interaction between liquid and laser decided the merits of propulsive performance. Torsion pendulum device was used to measure the micro-impulse. Monopropellant gel propellant, GAP and glycerol were used as propellant. Impulse and impulse coupling coefficient were measured under different laser energy. GAP obtained higher impulse coupling coefficient and was further studied. The results show that impulse coupling characteristics of GAP are better. Impulse coupling coefficient is generally greater than 500 μN/W, maximum is 1 493.0 μN/W. However, specific impulse and ablation efficiency are relatively low. Maximum specific impulse is 140 s; maximum ablation efficiency is 37.6%.