The invention discloses a laser heating film fixing-based electret film preparation method. The method comprises the following steps: fixing a conductive substrate layer to spin coating, spraying or scrape coating equipment, and preparing proper electret nanoparticle suspension; uniformly covering the electret suspension by adjusting spin coating speed, spraying speed or a scrape coating thickness parameter, then evaporating solvent of the electret suspension and thereby forming an electret material layer of a certain thickness on the conductive substrate layer; irradiating laser to the surface of the electret material layer by using laser heating equipment, thereby melting electret nanoparticles by using the heat produced by laser irradiation and interconnecting to prepare the electret film product. Through the method, the electret film product with superior filming performance and low probability of cracking separation can be machined on the flexible conductive substrate, and no damage is caused to the conductive substrate layer; meanwhile the method has the characteristics of convenience in operation and control, low cost, suitability for large-scale production and the like.