NiCrBSiC laser clad coatings are fabricated on TC4 substrate using CW-CO2 laser. The influence of processing parameter on the microstructure and dilution rate of the coatings is examined. Under the same power density and irradiation time, the depth of substrate fusion is deeper, the dilution rate of the coatings is higher and the reinforcing phases are mainly TiB2 and TiC when the laser beam diameter is lager (D=6 mm). The depth of substrate fusion is shallower, the dilution rate of the coatings is lower and the reinforcing phases are mainly CrB and small amount of M23(CB)6 and TiC when the laser beam diameter is smaller (D=3 mm).