In order to ensure the safety performance of lithium-ion power batteries and extend their cyclic service life, a battery thermal management system has thus been desinged based on microchannel liquid cooling plates to cool lithium-ion prismatic batteries, followed by the establishment of a three-dimensional thermal model of the battery cooling system so as to study the effects of high discharge rate, coolant temperature, and inlet mass flow rate on the highest temperature and maximum temperature difference during battery discharge process. The results show that under the maximum rate discharge condition of 5C, the highest temperature of the lithium-ion battery pack is 301.942 K, with a temperature difference of 1.942 K, thus achieving the expected cooling effect. With the decrease of coolant temperature and the increase of inlet mass flow, the maximum temperature of the battery decreases. As the inlet mass flow rate increases, the cooling performance of the battery has been improved, with the trend gradually decreasing. When the coolant temperature is 296 K, the maximum temperature of the battery is 297.662 K, while the mass flow rate is 15×10-7 kg/s, the temperature difference is 4.407 K.