It has received extensive attention to modify polyolefin separator by boehmite coating for the improvement of thermal stability and electrolyte wettability, but how to affect the electrochemical performance of the boehmite- coated separators is unclear. In this work, boehmite nanosheets with a mean particle size of 150 nm were synthesized by a simple hydrothermal method, and these nanosheets were coated on the surface of polyethylene (PE) separator by a scraper. The boehmite nanosheet-coated separator has porosity of 46.6%, electrolyte uptake of 138.9%, ionic conductivity of 0.47 mS/cm, and lithium-ion transference number of 0.42. The battery assembled with this separator exhibits good cycling stability, retaining 93.7% discharge specific capacity after 100 cycles at 1C (1C= 150 mA/g). Meanwhile, the boehmite nanosheet-modified separator has a uniformly distributed pore structure, which optimizes the lithium-ion transport flux and suppresses the formation of lithium dendrites.