The battery thermal management system (BTMS) using a unidirectional cooling strategy for a battery pack would cause the temperature gradient between the battery cells located at the inlet and outlet of the duct, which would reduce the temperature uniformity of the battery module. In order to solve the problem, the reciprocating cooling strategy was introduced in this paper to study the effect of switching time (τ) on the temperature uniformity of the battery module. Based on this, the flat heat pipe was combined with liquid cooling, in which the efficient heat transfer performance of the flat heat pipe could transfer the heat of the battery cells to the liquid. Using CFD to simulate the proposed BTMS, the result showed that the reciprocating cooling strategy could improve the temperature performance of the BTMS.