The invention discloses a heat radiating method and mechanism of an electric automobile battery box. The heat radiating method comprises the following steps: introducing natural air outside an automobile to radiate heat when the temperature in the battery box exceeds the preset temperature T2; radiating heat by extracting air-conditioning cold air in the automobile when the temperature in the battery box exceeds the preset temperature T4, wherein T4>T2; and stopping extracting the air-conditioning cold air in the automobile when the air-conditioning cold air is subjected to heat radiation, so that the temperature decreases and does not exceed the preset temperature T3 which is lower than T4 and higher than T2, and introducing natural air outside the automobile to radiate heat. The heat radiation method can play a better heat radiation effect on the battery box, does not waste energy, and meanwhile does not affect the environment in the automobile.