A ternary polyaniline/sulfur/acetylene black (PANi@S-C) composite cathode with variable PANi content has been synthesized by a continuous two-step liquid phase route. Different ratios of the PANi@S-C composite are characterized by SEM, TEM, FTIR, XRD and electrochemical methods. The conductive polyaniline plays multiple roles in the composite, acting as a conducting additive and a porous adsorbing agent. It is uniformly coated onto the surface of a S-C composite powder to form a core/shell structure, which significantly enhances the electrochemical performance and cycle life of the sulfur cells. The PANi@S-C composite with 12.5wt% PANi presents optimum electrochemical performance, where the initial discharge specific capacity is 1257mAhg−1 and remains ∼600mAhg−1 after 100 cycles at 0.16mAcm−2. After a rate test from 0.1 to 1mAcm−2, the cell remained at ∼600mAhg−1 sulfur after 50 cycles when the current density returned to 0.1mAcm−2.