Objective To improve the properties of Ni-P/nano-WC composite coatings. Methods Electro brush plating was used for co-deposition of Ni-P and nano-WC powder on 40Cr surface to form nano-particle reinforced composite coating. The coating was secondly reinforced by electric contact strengthening (ECS). The microstructures and properties of composite coatings were investigated by optical microscopy, field emission scanning electron microscopy (FESEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD) and Vickers hardness analysis. The rolling wear test was used to analyze the wear resistance of strengthened/unstrengthened composite coatings. Results The cracks and pores of composite coatings were reduced after ECS. Furthermore, the composite coating and the substrate were weld under high temperature and pressure environment. The XRD analysis presented that the size of gain of composite coating was refined which was reduced from 35.35 nm to 26.28 nm. With the increase of contacting electric current, the hardness of composite coating was gradually elevated. The average hardness of coatings was increased from 637HV0.1 to 886HV0.1 through the strengthening of electric current of 20 kA. Hence, the coating hardness distribution was more uniform. After 4-hour rolling wear test, the results showed that with the increase of contacting current, the weight losses of samples was gradually reduced. The weight loss of Ni-P/nano-WC composite coatings after 20 kA ECS was 503 mg which was 40% lower than the unstrengthened composite coatings. Conclusion The ECS can effectively improve the microstructure and properties of Ni-P/nano-WC composite coating. The bonding between the composite coating and the 40Cr substrate was changed from mechanical bonding to metallurgical bonding, at the same time, the wear resistance was improved.