The discharge–charge process of the porous sulfur/carbon nanocomposite cathode has been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), electrochemical impedance spectroscopy (EIS), and energy-dispersive X-ray spectroscopy (EDS). The results indicate that the porous nanocomposite enhances the electrolyte infiltrate into the cathode materials evenly, has a good capability of confining the soluble polysulfides and preventing the aggregation of insoluble Li2S. The regenerated elemental sulfur of the porous sulfur/carbon nanocomposite cathode exists in nano-size particles in the pore and the resistance decreases compared with the original cathode. Moreover, the porous nanocomposite realizes the micro-reactors during the discharge–charge process and can accommodate the volume change which is benefit for stabilization of the cathode during the electrochemical reaction.