With the development of electric vehicles, much attention has been paid to the thermal management of batteries. The liquid cooling has been increasingly used instead of other cooling methods, such as air cooling and phase change material cooling. In this article, a lithium iron phosphate battery was used to design a standard module including two cooling plates. A single battery numerical model was first created and verified as the basis of the module heat transfer model. Orthogonal experimental design method was adopted in the module thermal model to optimize the main parameters in the module: Battery gap, the cross-section size, and the number of coolant channels of the cooling plate. The Surrogate Model was then utilized to further optimize geometry of the cooling plate. Finally, the optimized geometry was rebuilt in the module thermal model for analysis. The comparison showed that the maximum and minimum temperature difference in the cooling plate was reduced by 9.5% and the pressure drop was reduced by 16.88%. It was found that the battery temperature difference and the pressure drop decreased with the increase of the cross-section and number of the coolant channel when the coolant flow rate was constant at the inlet.