In order to realize high efficiency and lightweight of battery thermal management (BTM), we designed a new liquid flow heat exchange structure which used flat tube bundle and graphite layer with high thermal conductivity. In different battery pack cooling processes, series of experiment were conducted to investigate basic heat transfer characteristics include temperature variation, temperature uniformity, thermal response and temperature fluctuation. The experimental results showed that the designed structure not only ensured cooling effect and temperature uniformity of battery pack, but also reduced volume and weight of liquid flow. At the same time, through adopting variable temperature cascade cooling method, cold shock were alleviative and temperature uniformity was promotion during battery pack cooling process. In addition, battery cooling effect was not sensitive to variation of liquid flow within experimental conditions, and this characteristic will facilitated to achieve low flow resistance and low pump power consumption.