The nuclear magnetic resonance (NMR) technique gives insight into the local information in a crystal structure, while Rietveld refinement of powder X-ray diffraction (PXRD) sketches out the framework of a crystal lattice. In this work, first-principles calculations were combined with the NMR technique and Rietveld refinement to explore the disordered crystal structure of aluminum oxynitride ( γ-alon). The theoretical NMR parameters predicted by the GIPAW algorithm were used to facilitate the analytical investigation on 27Al NMR spectra of γ-alon. The experimental δiso, CQ, and η of 27Al show small discrepancies with theoretical model. The occupancies of aluminum at disordered 8a and 16d positions, determined from relative integration of peaks in 27Al NMR spectra, were used in the Rietveld structure refinement of γ-alon. This work provided a powerful and accessible strategy to precisely understand crystal structure of novel materials with multiple disorder.