Activated carbon-CNT/sulfur composite cathode material for lithium-ion battery was prepared by melting method in a sealed FTPE reactor. Further, the composite was modified by PEG-coating, and the cathode composite material of C-CNT/S (PEG) was obtained. X-ray diffraction (XRD) analysis showed that the C-CNT/S (PEG) composite had an amorphous structure, and the sulfur was dispersed into the microspores of carbon material. Scanning electron microscopy (SEM) tests indicated that the CNT was uniformly dispersed in the composite, which formed a three-dimensional conductive structure. Discharge capacity tests showed the addition of CNT improve the discharge capacity of the composite. The first discharge capacity of PEG-coated composite (C-CNT/S (PEG)) was up to 1371.1mAh/g and the discharge capacity remained to be 662.8mAh/g after 50 cycles. The results demonstrated that the addition of CNT and PEG-coating can greatly improve the electrochemical performance of activated carbon/sulfur cathode materials.