Abstract: This paper introduced the main functions and properties of lithium ion battery separators and also described their production methods and preparation principles, which included coextrusion, coating, hot rolling, electrospinning and gel filling. To meet the high requirements in heat resistance, electrolyte wettability and mechanical properties in the power lithium ion battery, the research results from the co-extrusion, coating, hot-rolling, electrospinning and gel filling process for composite separators were overviewed. The features and applications of the composite separators were introduced. Finally, the development prospect of separators was brought out.