The work aims to address the issues of large temperature differences and high energy consumption during the charging and discharging processes of lithium-ion battery packs, and to ensure that the battery packs operate within an appropriate temperature range. A flat heat pipe-liquid cooling hybrid battery cooling system was designed. Through the establishment of a thermal-fluid coupling finite element model, the cooling process of power batteries under different cooling fluid flow rates, battery discharge rates, and heat pipe dimensions was simulated and analyzed. At an ambient temperature of 20 ℃, when the cooling fluid flow rate was 0.02 m/s, the maximum temperature at the center of the battery decreased by 17.9 ℃ compared to that under no cooling system. During 3C rate discharge, the maximum temperature of the battery in the flat heat pipe-liquid cooling hybrid battery cooling system was 37.3 ℃, which was 14.2 ℃ lower than that of liquid cooling alone. When the heat pipe length was 200 mm, the maximum temperature at the center of the battery decreased by 31.5%. The flat heat pipe-liquid cooling hybrid cooling system effectively reduces the temperature of power batteries during operation, improves the temperature uniformity of the batteries, and reduces the possibility of thermal runaway caused by overheating in certain parts of the battery.