A multi-step reaction route was developed to synthesize boron nitride(BN) nanoparticles via the reaction between NaN3 and BCl3 in a benzene-thermal solution.By means of this route,the crystallinity of BN nanoparticles was improved via increasing the reaction steps.Meanwhile,a phase transformation from hexagonal BN(hBN) or turbostratic BN(tBN) to cubic BN(cBN) occurred,resulting in the increase of cBN content.Moreover,the content of cBN also slightly increased when the temperature was elevated from 265℃ to 280 ℃.