Abstract: In order to effectively control the maximum temperature and temperature difference of the battery, a cooling system is designed, which adopts an innovative spiral fin and combines it with an immersion cooling system. The effects of fin width, spiral number and flow rate of cooling medium on battery heat dissipation are studied. The results show that the temperature of the battery can be effectively reduced by increasing the fin width and spiral number. When the fin width increases from 2 mm to 8 mm, the maximum temperature of the battery decreases by 1.33 ℃. On this basis, the influence of the number of helical turns is further discussed. When the number of helical turns increases from 2 Q to 8 Q, the maximum temperature of the battery decreases by 0.84 ℃. When the fin width is 8 mm and the spiral number is 6 Q, the influence of the flow rate of cooling medium on the temperature of the battery is further studied. When the flow rate is 0.064 m/s, the maximum temperature of the battery is only 28.64 ℃. When the flow rate is more than 0.024 m/s, the temperature difference of the battery increases first and then decreases, both of which are less than 5 ℃. The pressure drop range is 10.96-93.73 Pa. The above findings provide more insights into the cooling system of oil-immersed batteries, and prove that the addition of fins in the system can effectively reduce the maximum temperature difference between the battery and the temperature difference, which provides a reference for enhancing the heat transfer design of the system.