Due to the fact that the thermal management system of lithium-ion batteries is the key to the improvement of cooling efficiency, a corresponding numerical model has been established to optimize the design of the liquid cooling channel pipeline for vehicle lithium-ion batteries, with the feasibility of the numerical model to be demonstrated through experimental verification. The results show that under a high-rate discharge, the microchannel cooling system can reduce the temperature difference of the battery from 9.74 K to 4.71 K and the maximum temperature from 309.74 K to 305.13 K, both within the optimal operating range. A research on the coolant temperature reveals that an improvement of the temperature environment of the battery cannot be achieved by simply reducing the coolant temperature. A suitable temperature is needed to ensure the temperature difference of the battery, with a linear relationship between the coolant temperature and the temperature difference of the battery. Meanwhile, the temperature difference of the battery increases as the coolant temperature decreases.