Pyrolysis experiments of melamine were carried out under high pressure of 5 GPa and different temperatures. The crystal structure, chemical bonding, and composition of the melamine pyrolysate were studied by X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray energy-dispersive analysis (EDX), and combustion elemental analysis. A new C-N-H phase was found in the pyrolysate at 5 GPa and 800 degrees C. The structure is tentatively indexed as a monoclinic symmetry, with the following lattice parameters: a = 8.5368 (+/- 0.0009)angstrom, b = 9.1153 (+/-0.0010)angstrom, c = 10.2440 (+/- 0.0011)angstrom, alpha = gamma = 90 degrees, and beta = 95.5696 (+/- 0.0016). The photoluminescence behavior of the pyrolysates was investigated. A blue emission at 421 nm for the C-N-H phase was observed under the ultraviolet light excitation of 365 nm.