Lithium‐sulfur batteries (LSB) are one of the potential candidates for the next generation of electrochemical energy storage technology, due to their advantages of high theoretical capacity and high energy density. However, sluggish redox kinetics and the shuttle effect of polysulfides in the cyclic process lead to low sulfur utilization, severe polarization and poor cyclic stability. Herein, an SnS modified porous carbon nanosheet (SnS/PCNS) hybrid material is synthesized by a simple hydrothermal method and used to modify the separator of the LSB for the first time. Specifically, SnS/PCNS can not only adsorb polysulfides, but also enhance the redox reaction of polysulfides. In addition, SnS/PCNS are shown to promote rapid nucleation and uniform deposition of Li2S, and to improve the discharge capacity and heighten cyclic stability. The initial capacity is 1270 mAh g−1 at 0.5 C, the slow decay rate of each cycle is 0.039% at 1 C. When the sulfur loading is improved to 6 mg cm−2, the high reversible capacity is 955.3 mAh g−1 at 0.5 C. As a new polysulfides adsorbent, SnS provides a potential route for the commercialization of LSBs. A highly stable and long‐cycle life lithium‐sulfur battery is successfully achieved via a SnS and porous carbon nanosheet (PCNS) modified separator, in which the SnS/PCNS has a strong adsorption effect on polysulfide, together with good catalytic activity and high conductivity.