All inorganic perovskite (CsPbX₃) nanocrystals has wide applications in the field of optoelectronic devices due to its excellent photoelectric characteristics, however, stability is still the bottleneck restricting its development. Combining with the current research progress, the BN/CsPbX₃ composite nanocrystals phosphors was synthesized via all-solid-state reactions. During the process, parameters of ball milling, ratio of reactants and other reaction conditions were optimized, thus the BN/CsPbX₃ composite nanocrystals can be stable in the air for more than 60 days. Its luminescence wavelength can cover the range of 417-680 nm with full width at half maximum of 23-47 nm, showing high color purity, and was further used in white LED with high stability and luminance. After placed in the atmosphere for a month, the attenuation of LED luminance is only about 0.7%, and less than 4% deterioration was observed after continuous work of 2 h, showing great working stability.