In situ NbC reinforced CoCrCuFeNiMn(NbC)x (x=0, 0.05, 0.1, 0.2, 0.3, 0.4) high entropy alloys were prepared by plasma cladding on the Q235 steel. The phase constitution, microstructure and microhardness of the cladding layer were investigated. The results show that C and Nb addition doesn’t cause complex phase and the diffraction peaks are composed of fcc1, fcc2 and NbC phase. Most of the NbC is deposited in the interdendrite and a few of them is dendrite. The shape of NbC is related to its content. When x is small, NbC is granular. When x is large, NbC is granular, strip and cross dendritic. Compared with that of the matrix, the hardness of in situ high entropy alloy matrix composite is significantly improved. The hardness of the cladding layer is increased with more NbC in a certain range (x=0~0.4)