The embodiment of the invention provides a power battery thermal management system including: a battery cooling unit and a battery fire extinguishing unit. In the battery cooling unit, an air cooler outputs cooled gaseous carbon dioxide to the air inlet of an ejector, the ejector inputs the gaseous carbon dioxide entering from the air inlet and the gaseous carbon dioxide injected from an injectingport into a gas-liquid separator, the gas-liquid separator outputs the separated liquid carbon dioxide from a liquid channel port and an expansion valve to a battery cooling evaporator, and the battery cooling evaporator cools the power battery pack by the liquid carbon dioxide. When the power battery pack is on fire, the battery cooling unit stops working. In the battery fire extinguishing unit,the gas-liquid separator outputs the liquid carbon dioxide from a liquid channel port and an electric valve to a nozzle, and the nozzle extinguishes the fire and cools the power battery pack by ejecting the liquid carbon dioxide. The power battery thermal management system handles the thermal runaway of the power battery while cooling the power battery.