In this article, we propose a trilayer graphene/polypropylene/Al2O3 (GPA) separator with dual function for high performance lithium–sulfur (Li–S) batteries. Graphene is coated on one side of polypropylene (PP) separator, which functions as a conductive layer and an electrolyte reservoir that allows for rapid electron and ion transport. Then Al2O3 particles are coated on the other side to further enhance thermal stability and safety of the graphene coated polypropylene (GCP) separator, which are touched with lithium metal anode in the Li–S battery. The GPA separator shows good thermal stability after heating at 157 °C for 10 min while both GCP and PP separators showing an obvious shrinkage about 10%. The initial discharge specific capacity of Li–S coin cell with a GPA separator could reach 1067.7 mAh g−1 at 0.2C. After 100 discharge/charge cycles, it can still deliver a reversible capacity of as high as 804.4 mAh g−1 with 75% capacity retention. The pouch cells further confirm that the trilayer design has great promise towards practical applications.