In order to meet the needs of actual working conditions and people's expectations, electric vehicles using lithium ion batteries as power sources are not completely comparable to traditional fuel vehicles in terms of endurance mileage and driving performance. The main technologies of battery thermal management system are summarized, and the research status of air cooling, liquid cooling and phase change material cooling and heat generation characteristics of batteries are summarized. Based on CFD (Computational Fluid Dynamics) analysis method, the model of liquid cooling and heat dissipation system of batteries is established, and the flow of cold fluid in cooling channel and the temperature change of batteries are analyzed. Based on the simulation results of the original model, the existing problems are analyzed and the cooling passage structure of the cooling system is optimized. The temperature field and flow field of the improved scheme are simulated, analyzed and compared. The results show that, compared with other kinds of batteries, lithium ion batteries have many advantages, such as high voltage, light weight and no pollution. However, the working performance of lithium ion is closely related to the working temperature. When the working temperature is too high, the working safety of lithium ion is not guaranteed; when the working temperature is too low, the chemical reaction rate decreases, and the capacity of lithium ion batteries decreases, which has adverse effects on the endurance mileage and driving performance. Therefore, it is necessary to study the temperature field control of batteries to ensure the normal operation of electric vehicles.