Abstract: A novel precursor for BCN compound, C3H6N6(H3BO3)2, was synthesized with C3H6N6 melamine and H3BO3 as raw materials in aqueous solution. The precursor was characterized by elementary analysis, XRD, FT-IR, electrospray mass spectrometry and single crystal X-ray diffraction. It revealed that the precursor contained the characteristic groups of C3H6N6 and H3BO3 such as triazine ring, NH2, and B—OH. The precursor crystallized in monoclinic space group P2l/c, with the cell parameters a=0.35970(7) nm, b=2.0105(4) nm, c=1.4112(3) nm, β=92.07(3)°, Z=4. One crystallographically distinct C3H6N6 molecule and two H3BO3 molecules constituted the asymmetric unit of the precursor. A 3D supramolecular network was constructed by different hydrogen-bonding interactions between C3H6N6 and H3BO3 molecules. The precursor was further pyrolyzed at 1900 ℃ under flowing N2 atmosphere. XRD and XPS analysis were applied for the characterization of the pyrolysis product. The results indicated that a new BCN ternary compound with turbostratic graphite structure was obtained. B—N, B—C, and C—N chemical bonds were established and there was no phase separation between graphite and h-BN, which suggests an atomic-level hybrid of B, C, and N elements in the compound. The BCN compound has lower carbon content and its empirical formula can be expressed as B3CN3.