As the result of combustion reaction in Al-Al2O3-N2 system, AlON phase can be synthesized in the range of initial nitrogen pressure, from 1 to 5 MPa. On the occasion of rm = 0.3, the unreacted Al was detected in the case of 1 MPa of PN2. Its intensity decreases with an increase of nitrogen pressure. Ultimately, no peak of Al was observed in the product at nitrogen pressure of 5 MPa. In addition, the peak intensity of AlON in the products increases proportionally with the nitrogen pressure, while the intensities of AlN and Al2O3 decrease slightly with an increase of nitrogen pressure. The formation of AlON may be induced by successive two reactions. The former is the formation of AlN, and the latter is the reaction between AlN and Al2O3 in the after-burning period sustaining high temperature.