Three-dimensionally macroporous (3DM) polymer membranes based on poly(vinylidene ﬂuoride-co-hexaﬂuropropylene) (P(VdF-HFP)) are simply prepared through etching calcium carbonate (CaCO3) hard template, which was filled in the polymer matrix previously. It is observed, from the SEM images, that some macropores within the obtained 3DM polymer membrane interconnect through many little holes, which would leave the continuous channels for ion transportation in the resultant polymer electrolyte. The 3DM polymer membrane made from the casting solution, in which the mass ratio of CaCO3 to P(VdF-HFP) is 2:1, has a porosity of 73.6%. The resultant 3DM polymer electrolyte (3DMPE) possesses high ionic conductivity of 1.38×10−3 S cm−1 at room temperature and low activation energy for ion transportation of 6.85kJmol−1. The assembled Li/LiMn2O4 cells exhibit good rate and cycling capabilities when using this 3DMPE membrane as a separator. The results suggest the 3DMPE could be promisingly applied in lithium-ion batteries.