Abstract: Polyvinylidene fluoride/polymethyl methacrylate (PVDF/PMMA) composite films prepared by electrospinning were mechanically modified by heat treatment process. The effects of temperature and pressure on the mechanical properties of the composite films were studied. The mechanical properties, ionic conductivities and cycling properties of the composite membranes were compared with those of commercial films Celgard 2400. The results show that the tensile strength of PVDF/PMMA composite film is 19.0 MPa after a treatment at 145℃ and under a pressure of 0.05 MPa, which is 10 times higher than that of the composite film without pressure treatment; the ionic conductivity of PVDF/PMMA composite film at room temperature is 1.180 mS/cm, which is 187% higher than that of commercial film. The specific capacity of button cell assembled by PVDF/PMMA composite film is 140 (mA·h)/g at 0.2 C ratio and 130 (mA·h)/g at 1 C ratio, compared to commercial film at the same rate of discharge. The film presented better cycle performance at 5 C ratio.