Eelectrodeposited black Cr-C nano-composite coating was prepared on the steel substrate and the effects of current density on the properties of the composite coating were studied in the present paper. The surface morphology and phase composition of the composite coatings were analyzed by means of scanning electronic microscopy (SEM) and X-ray diffractometer (XRD). Microhardness was determined by micrometer and the wear resistance of the coatings was evaluated by CETR using a universal materials tester (UMT). The results showed that formed under the condition of current density of 100A/dm2, temperature of 15°C, and the optimum particle content in electrolyte was 10g/l. The maximum microhardness of black Cr-C nano-composite coating was 10.8 Gpa, simutaneously, the wearing resistance of the coating improved significantly compared to the steel substrate.