The practical application of LithiumSulfur battery is limited due to its rapid capacity fading and early battery failure caused by the shuttling of soluble polysulfide. Thus, the key to improve the performance of a LithiumSulfur battery is to suppress the shuttling effect. Herein, we report a NbN modified PP separator with high performance for LithiumSulfur battery applications. The NbN functionalized layer of the separator can strongly interact with soluble polysulfide species, as demonstrated by both experimental investigation and theoretical verification. As a result of the high polysulfide affinity, the composite separator effectively prevents the shuttling of soluble polysulfide through the separator. Besides, the high electrolyte wettability of NbN modification layer lowers the resistance of Li+ transport through the separator. Due to these favorable features, LithiumSulfur battery assembled with the multifunctional NbN modified separator exhibits excellent cycling performance with a reversible capacity of 554.6 mAh g−1 after 200 cycles at 0.2C. The significantly improved rate performance of the battery based on the modified separator is also demonstrated. Our results show that NbN is a promising material for the modification of separators in LithiumSulfur battery and the strategy of separator engineering is effective for improving the performance of LithiumSulfur battery.