To expand the application of CoCrNi-based medium-entropy alloy (MEA) coatings in marine engineering, laser cladding technology was employed to prepare CoCrNi+x wt% NbC (x = 0, 5, 10, and 15) composite coatings. A systematic study was conducted on the effects of NbC on the microstructure, mechanical properties, and corrosion resistance of CoCrNi MEA coatings, while also analyzing the distribution of NbC within the coatings and its formation mechanism. Microstructural analysis showed that NbC addition transformed the MEA coating phase composition from single-face-centered cubic (FCC) to dual-phase FCC + NbC, along with significant grain refinement. Mechanical testing results show that NbC doping induces solid solution strengthening, grain refinement strengthening, and dispersion strengthening effects in the coating. Under the synergistic action of these strengthening mechanisms, the microhardness of the coating increases with increasing NbC content and reaches a peak when the NbC content reaches 15 wt%. When the NbC addition is 10 wt%, the coating exhibits optimal wear resistance, with a wear rate of only 19.55 % that of the CoCrNi MEA coating without NbC addition. This strengthening effect stems from the uniformly dispersed NbC particles effectively bearing the load, significantly inhibiting direct contact between the friction pair and the coating. At this point, the wear mechanism is adhesive wear and abrasive wear. However, when the NbC addition exceeds 15 wt%, NbC particles agglomerate, leading to a decrease in the coating's wear resistance. Electrochemical tests show that introducing NbC promotes forming Nb 5+ ions, significantly improves passivation film formation rate, and enhances its corrosion resistance. Additionally, during the corrosion process, NbC can effectively impede penetration of corrosive media, thereby enhancing the coating's corrosion resistance. After comprehensively evaluating all properties, the CoCrNi +15 wt% NbC coating exhibits optimal performance advantages.