The invention relates to an energy conversion device and a working method thereof. The energy conversion device comprises an energy storage control module, an energy charging module, an energy storagemodule, a constant current voltage limiting module and a reference module. By means of a temperature difference power generation mode, the heat energy generated by an electric appliance is utilized;and when the electric appliance needs to be charged, a charging circuit is communicated, the charging circuit is disconnected after the electric appliance is fully charged, so that the heat emitted bythe electric appliance can be effectively utilized.