An electric vehicle thermal management system and method based on a self-circulating gas-liquid phase change cold plate are disclosed. A top cover, a first heat exchanger, a battery case partition and a battery case bottom plate are arranged in sequence from top to bottom, a top heat exchanging chamber is formed between an upper heat exchanging surface of the first heat exchanger and the top cover; the battery case partition is of a square wave-like structure, a working medium chamber is formed between a top of the battery case partition and a lower heat exchanging surface of the first heat exchanger, the working medium chamber is filled with a gas-liquid phase change working medium, and a plurality of battery chambers are formed between the bottom of the battery case partition and the battery case bottom plate.