The formation time and evolution process of FeSi5Cr5.5/SiO2 core-shell structure during the fluidized bed chemical vapor deposition were studied with tetraethoxysilane as the precursor of SiO2 insulation and FeSi5Cr5.5 spherical particles as the substrate. The microscopic characteristics of particle samples before and after deposition were characterized by X-ray diffraction, field-emission scanning electron microscopy and X-ray photoelectron spectroscopy. The magnetic hysteresis loops and resistivity of particle samples before and after deposition were measured using vibrating sample magnetometer and four point probe instrument. The results showed that it took 30 minutes at a minimum to completely convert from FeSi5Cr5.5 particles to FeSi5Cr5.5/SiO2 core-shell structure particles according to the three-dimensional island nucleation model during the fluidized bed chemical vapor deposition. There were four and five categories of silicon and oxygen electron structure in the FeSi5Cr5.5/SiO2 core-shell structure. The resistivity of FeSi5Cr5.5/SiO2 core-shell structure particles increased three and four orders of magnitude than that of FeSi5Cr5.5 particles, while the values of saturation flux density declined slightly.