An intermediate-frequency furnace was used for continuous production of hexagonal boron nitride (h-BN) by heating a mixture of C3N6H6 and H3BO3 in a flowing nitrogen gas at 1800-1950 degrees C. The products were examined by XRD, Raman, FTIR, and SEM. The results indicate the as-synthesized products are h-BN flakes with a purity of 98.73 wt %. A possible reaction mechanism is discussed.