Vibration and ablation are two main mechanisms of pulsed laser cleaning insulator surface pollution, but the actual mechanism will be different under different laser parameters. A thermo-stress coupled finite element model was established by COMSOL to simulate temperature and stress fields, and the vibration and ablation mechanism and cleaning effect of pulse laser scanning with different pulse power during one cycle were explored. The feasibility of simulation results was verified by laser cleaning experiment. The simulation results show that the pollution removal threshold of vibration and ablation mechanism is about 123 W, and both vibration and ablation increase with the increase of pulse power. At 150 W, the cleaning depth is 40% of the pollution thickness, and at 200 W, it reaches 92% of the pollution thickness. At 250 W, the cleaning mechanism reaches the critical state and the cleaning depth reaches the cleaning thickness. Above 250 W, the ablative mechanism dominates. Taking 300 W as an example, the insulator has obvious damage. Experimental results show that when the power of the equipment is 200 W, the pulsed laser can remove the pollution on the insulator surface obviously, and the pollution on the insulator surface bounces under the force and has obvious gasification phenomenon. Only a small amount of pollution remained in the insulator base, and no damage was observed.