The work aims to study the effects of chromium carbide content and wear load on wear resistance of the composite coating and the wear mechanisms under different loads. Metal composite coatings were fabricated with Ni-based (Ni55) mixed powder with NiCr-Cr3C2 mass fraction of 10%, 20%, 30%, 40% and 50% by plasma transferred arc (PTA) cladding technology. The phase compositions of these coatings were detected and analyzed by XRD and SEM and the wear resistance under different loads was tested by Rtec universal friction and wear tester. The microstructures, friction coefficient, wear body and wear surface morphologies of the coatings were analyzed by comparison to study the effects of chromium carbide content and wear load on wear resistance of the composite coating. NiCr-Cr3C2 was melted during cladding. By XRD, the carbide in the coating mainly consisted of Cr7C3 and other main phases included Cr3C2, Cr23C6, Cr5B3 and Ni3Si. The microhardness and wear resistance of the coatings gradually increased with increasing abundance of the chromium carbide. The maximum microhardness of the coatings was up to 1500HV, and the wear resistance was enhanced 2~16 times over that of the Q235 substrate. When load was lower than 80 N, abrasive wear was mainly wear mechanism, while when the load reached 100 N, the wear mechanism changed from abrasive wear to adhesive wear. The wear mechanism of S5 was fatigue wear and abrasive wear. The wear resistance of composite coating increases continuously due to the increasing chromium carbide and the wear mechanism changes as the wear load increases.