A safe and high-performance electrothermal heater needs a lower operating voltage to produce heat for long time and high efficiency. The Gr-CNTs (graphene-carbon nanotubes) composite film and AgNWs (Siliver nanowires) dispersions had been prepared and AgNWs were successfully coated on this composite films. The electrothermal performance of composite films with different carbon nanotubes contents, polymer additions and coating AgNWs had been investigated. The maximum heating temperature decreases with the content of polymer increases. In addition, the maximum temperature increases with addition of carbon nanotubes. The sheet resistance gradually decreases with improving AgNWs coated amount and the sheet resistance changes little with the bending times in a whole. The microstucture of composite films coated with AgNWs revealed that AgNWs filled the holes on the surface of composite films. Besides, the electrothermal efficiency, heating rate and cooling rate were significantly improved. For the electrothermal performance of the composite film coated with AgNWs only on the contact surface, the electrothermal efficiency, heating rate and cooling rate were also significantly improved compared with those of the composite film without AgNWs coating. Therefore, composite films coating with AgNWs is one effective method to significantly improve the electrothermal performance for Gr composite film.