In this work, the poly(vinylidene difluoride hexafluoropropylene) (PVdF-HFP) membranes with tuned pore structure are prepared and used as a separator for the lithium–oxygen battery. Both oxygen and argon plasma treatments are used to tune the surface pore size and density of the membrane. The discharge capacity of the Li–O2 battery increases with the pore size and density of the membrane, nearly maximal capacity is achieved with a pore size of ca. 1.48 μm. More importantly, the Li–O2 battery using the PVdF-HFP membrane with tuned pore structure exhibits a significantly enhanced rate performance, probably due to a faster Li+ ion transport across the membrane. The highest discharge capacity of 466.1 mAh g−1 is achieved at a current density of 5 mA cm−2 for the Li–O2 battery with the PVdF-HFP thickness of 110 μm and pore size of 1.48 μm. Such a discharge capacity is about 10 times higher than that using commercial PP/PE/PP membrane. To our knowledge, it is the first report that the regulation of the pore structure of separator could significantly improve the rate performance of the Li–O2 battery, which probably provides a new way to solve the low rate characteristics for non-aqueous Li–O2 battery.