Polypyrrole nanotube film (PNTF) is self-assembled with a simple method from PPy nano-tubes. Consequently, PNTF is sandwiched between sulfur cathode and separator to act as the functional interlayer for Li–S battery. Because of the adsorption effect between PPy and lithium polysulfides and the conductivity of PPy films, the polymer interlayer can not only decrease the polarization of sulfur cathode significantly, but also suppress shuttle effect and the redistribution of active material during charge/discharge process effectively. Li–S battery with the functional interlayer shows an encouraging electrochemical performance. With approximately 2.5–3 mg cm−2 sulfur loading on the electrode, the initial discharge capacity is 1102 mAh g−1, and the capacity retains at 712 mAh g−1 after 300 cycles at 0.5C, and the coulombic efficiency increases to around 92% in the electrolyte without LiNO3.