A waste heat recovery system is provided. The system comprises: an appliance, a tank, a pump and a pipeline switch. The appliance comprises: a housing, a refrigeration module, a heat exchanger, and a circulating water pipe. The tank is for storing heat energy generated from the refrigeration module with water therein and/or pumping water having the saved heat energy to the circulating water pipe to heat a space provided in the appliance. The pipeline switch controls water flow between the tank, the heat exchanger and the circulating water pipe. The system allows the appliance therein to refrigerate, thaw, and/or cook food, and it reduces electric energy consumption.