Abstract: Five kinds of coatings have been prepared on the surface of 45CrNi steel plates using laser cladded technique by adding 0, 2.5 wt.%, 5 wt.%, 7.5 wt.% and 10 wt.% Mo into the NiCrBSi alloys.The effect of molybdenum on the crack sensibitities of laser cladded NiCrBSi alloy coatings of these five kinds of coatings were investigated by oil whiting test.Crack sensibitities are affected by the coefficient of thermal expansion of the coatings and the solidification characteristics and microstructures.The research results present that NiCrBSi alloy is very sensitive to cracking and many transverse macro cracks appear on the clad pass.While the sizes of dendrites and the carbides morphologies of eutectic microstructure of the coating with 5.0 wt.% of Mo are different frorn the others.Meanwhile, the coefficient of thermal expansion of the coating is decreased.Both of two effects are responsible for the reduction of crack sensibilities.