Abstract: In order to maintain the operating temperature of lithium ion battery packs in a reasonable and safe operating range, this paper proposes a linear quadratic regulator to control the maximum battery temperature, temperature difference and energy consumption of the liquid-cooling battery thermal management system. By inputting the current into a battery under the operation condition of NEDC and US06, heat generation models are built by using Matlab-Simulink and Amesim software. The battery temperature and temperature difference curves are obtained and the reliability of the models are validated. Under 3C charging and -NEDC discharging conditions, a comparative study of the thermal management capacity is carried out among LQR, PID and constant flow rate control. The results show that the battery thermal management system based on LQR control has a good response speed and stability. By comparing the effect of the three controllers on the maximum temperature difference of BTMS, it is found that the LQR controller exhibits the best control capacity when the liquid-cooling channels of the battery pack are arranged in reverse. Compared with PID and the constant current controller, the LQR controller can reduce cooling energy consumption.