The polysulfide shuttle reaction has severely limited practical applications of Li-S batteries. Recently, functional materials that can chemically adsorb polysulfide show significant enhancement in cycling stability and Coulombic efficiency. However, the mechanism of the chemisorption and the control factors governing the chemisorption are still not fully understood. Here, it is demonstrated for the first time that the surface acidity of the host material plays a crucial role in the chemisorption of polysulfide. By tailoring the surface acidity of TiO2 via heteroatom doping, the polysulfide-TiO2 interaction can be fortified and thus significantly the capacity fading be reduced to 0.04% per cycle. The discovery presented here sheds light on the mechanism of this interfacial phenomenon, and opens a new avenue that can lead to a practical sulfur/host composite cathode.