In this paper, the experimental results of synthesizing BN nanocrystals by both solvothermal and hydrothermal routes have been briefly reviewed. At the end of this paper, the results of utilizing BN nanocrystals as the catalyst for the "polymerization" of benzene are also discussed. The full text contains five parts. 1. Introduction to the synthesis of cubic boron nitride. a. Results of synthesizing cBN by high temperature & high pressure route; b. Results of the synthesis of both hexagonal and cubic boron nitride by sovlothermal route. 2. Synthesis of BN nanocrystals by solvothermal route. a. Preparation of hBN nanocrystals by reacting BBr3 with Li3N; b. The reaction of BCl3 with Li3N for the synthesis of hBN and cBN and cBN nanorods; c. The preparation of hBN nanocrystals from BCl3 and NaN3. 3. Application of structural induction effect on controlling the phases in BN nanocrystals. a. Synthesis of cBN nanocrystals at medium temperature by the induction effect of bulk 316L stainless steel plates; b. Synthesis of cBN nanocrystals at 200°C under the structural induction effect of GaP nanocrystals; c. Preliminary comparison of the induction effects of GaP and Ni nanocrystals. 4. Synthesis of cBN nanocrystals by hydrothermal synthesis route. a. Synthesis of oBN and cBN by the reactions of NaN3, H3BO3 and P in aqueous solutions; b. Synthesis of cBN by the reactions of NaN3, H3BO3 and N2H4·H2O in aqueous solutions. 5. Comparison of the catalytic effects of hBN and AlN nanocrystals on the “polymerization” of benzene molecules.