The invention belongs to the technical field of lithium ion batteries, in particular to a polytetrafluoroethylene/polycarbonate composite separator for batteries, wherein the composite separator comprises 70 to 95 percent of polytetrafluoroethylene and 5 to 30 percent of polycarbonate in terms of mass fraction; Polycarbonate is aromatic polycarbonate; It was prepared by electrospinning. It has abundant pore structure and high porosity, good permeability, conducive to the absorption and retention of electrolyte, and conducive to the transport of ions in the diaphragm, improve the efficiency ofcharge and discharge lithium ion batteries. Therefore, the polytetrafluoroethylene/polycarbonate composite diaphragm for battery exhibits excellent air permeability and thermal stability, remarkably improves affinity with electrolyte, and is more excellent in contact angle and liquid absorption rate of electrolyte. The polytetrafluoroethylene/polycarbonate composite diaphragm for battery exhibitsexcellent air permeability and thermal stability.