Lithium-ion batteries, the heart of electric vehicles (EVs), are subject to capacity attenuation and lithium plating at low temperatures, which is essential to preheat lithium-ion batteries at low-temperature ambient. In this study, a battery thermal management system (BTMS) was established to achieve integration of preheating and cooling at the module level through a bent flat micro heat pipe array (FMHPA). As a thermal bridge, the bending FMHPAs realize the separation of the coolant and the battery, non-interference of preheating and cooling, and small space occupation. Heat transfer characteristics of bending FMHPA, preheating performance of the BTMS, and the effect of insulation shell were studied experimentally. Results showed that the effective thermal conductivity of Z-shape bending FMHPA is 15,741 Wm-1K−1. The temperature rise rate can reach about 1 ℃/min at the ambient temperatures of −20, −10 and 0 ℃. The temperature differences at both cell and module levels are kept within 5 ℃. The insulation shell with a thickness of 20 mm can increase the temperature rise rate and temperature difference at module level by 41% and 35%, respectively, but with no obvious influence on the active cooling effect at high-temperature ambient.