Abstract: Conductive sulfur-containing material (CSM), synthesized by simply heating a mixture of polyacrylonitrile (PAN) and elemental sulfur, and its composite with polyaniline (PAn) were used as the cathode material for rechargeable magnesium batteries. X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) spectroscopy measurements showed that the CSM consisted of a graphite-like microcrystal phase and an amorphous phase, with a dehydrapyrimidine-type matrix containing S—S bonds. When polyaniline was incorporated with CSM and Cu(II) was doped into the CSM/PAn composite, the specific discharge capacity and electrochemical reversibility were enhanced significantly. The composite exhibited a discharge capacity of 117.3 mAh·g-1 and the capacity retention remained at about 78% after twenty-two cycles, based on the second cycle discharge capacity. Here PAn functioned as both electrocatalyst and cathode material. At the same time, it improved the conductivity of the active CSM at a molecular level. The results of this study provided a new thought for structure design and development of a potential cathode material for rechargeable magnesium batteries.