In virtue of electron energy spectrometer, X-ray diffractometer and scanning electron microscope, the effects of rare earth yttrium on chemical composition and structure of the vacuum fusion sintering NiCrBSi alloy coating were studied. The results show that rare earth yttrium changes chemical component of alloy coating and hinders the dilution of Fe for NiCrBSi alloy coating owing to the diffusion of Fe atom in alloy coating from steel matrix. Rare earth yttrium makes Fe content in alloy coating decrease, eliminates needle phase of alloy coating mostly, and gets globular phase of alloy coating deposited and refined further. New second phases Cr7C3 and Ni2B are also precipitated from vacuum fusion sintering NiCrBSi alloy coating containing rare earth yttrium.