Abstract In this paper, thermal runaway test of lithium iron phosphate battery (LiFePO 4 /C) under overcharge condition was carried out. The temperature and its rise rate of three types of LiFePO4/C batteries (25 Ah, 60 Ah and 200 Ah) in the process of thermal runaway were compared and analyzed. The research shows that under the condition of 1C-rate overcharge, the starting temperature of the LiFePO4/C battery thermal runaway is about 116 °C - 131 °C, and its temperature rise rate of thermal runaway is about 3.01 °C/s - 5.82 °C/s. The highest temperature reached by thermal runaway has nothing to do with the battery capacity.