Electrochemical properties and performance of lithium/polymer electrolyte/composite sulfur cells are presented. The composite sulfur cathode prepared by two ways were characterized and compared by X-ray diffraction (XRD), thermogravimetry (TG), differential thermoanalysis (DTA) and scanning electron microscopy (SEM). The all-solid-state Li/S battery operated at 75°C with P(EO)20Li(CF3SO2)2N–10wt.%γ-LiAlO2 as electrolyte exhibited an average capacity of 290mAhg−1 for the sulfur melted together with poly(ethylene oxide) (PEO) during 50 cycles. The mechanisms for capacity degradation of the Li/S polymer battery were discussed.