Abstract: BN interfacial coatings were prepared on the surface of SiC fibers by chemical vapor infiltration (CVI). Then the coatings were heat-treated at several temperatures higher than the deposition temperature. The microstructure and chemical compositions of BN interfacial coatings were analyzed by scanning electron microscope, transmission electron microscope, Raman spectra, and X-ray photoelectron spectroscopy, and the phase stability of the coatings were studied. The results show that when BN interfacial coatings deposited at 850 ℃ were heat-treated at 1050, 1150 and 1250 ℃, respectively, BN was ordered and amorphous BN was transformed into hexagonal crystallographic phase. Moreover, the crystallinity of BN increased with the increase of heat-treatment temperature. The amorphous BN coatings without high temperature heat-treatment were partly reacted with air to form B₂O₃. This kind of BN coatings had poor phase stability in the range of room temperature to 1200 ℃. The coatings with high temperature heat-treatment were almost composed of BN, and there was no phase transformation from room temperature to 1200 ℃.