A shutdown-functionalized lithium-ion battery membrane plays an important part in preventing thermal runaway as batteries suffer an external short circuit, accidental overcharging, and abuse of battery pack. In this study, an isotactic polypropylene (iPP)/hydrogenated petroleum resin (HPR) + iPP/ iPP trilayer separator with shutdown property is prepared through a facile dry process with biaxial stretching. The shutdown function is obtained by the low softening temperature of HPR, which closes the microporous structure at a relatively low temperature. This trilayer separator has a similar porosity, Gurley value, and electrolyte uptake compared with the pure iPP separator at room temperature. When the temperature exceeds the softening point, HPR within the core layer melts to close the channels for Li-ion transport, causing micropores to collapse; meanwhile, the iPP skin layers hold the dimensional stability of the whole separator to prevent the internal short circuiting. In addition, electrochemical tests reveal that the interface impedance, ionic conductivity, and cycle performance of the iPP/HPR + iPP/iPP trilayer separator are similar to those of the pure iPP separator and commercial separator. The proposed method features simple techniques, environmental friendliness, and low manufacturing cost, which can offer new thoughts for the mass fabrication of high-function separators.