In this paper, boron-doped nanodiamond was prepared by high temperature vacuum diffusion methodat in a vacuum container. Thermogravimetric analyzer(TGA), X ray photoelectron spectroscopy(XPS), X ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), Raman spectroscopy, transmission electron microscope (TEM)were used for characterization of the prepared work. The results show that the products mainly contain C, O and B, and the mass fraction is 92.08%, 7.14%, 0.78%. In addition to diamond (111) _D and (220) _D diffraction peaks, there is also hexagonal diamond (1 0 0)_D diffraction peaks in XRD picture of boron-doped product. The introduction of B atoms results in an increase in the defects of nanodiamond, causing the G peak to move to 1620cm_-1. Boron atoms mainly exist in two forms of substitutional carbon atoms (C-B) bonds and bonds with the impurity elements (B-O) in the diamond lattice. The shape and morphology of boron-doped nano diamond particles have no obvious change. The particle size is 2~ 10nm and a small amount of cubic diamond exist. In conclusion, the initial oxidation temperature of boron-doped nano diamond increases by 175℃, the oxidation rate is slow and the thermal stability is improved.