Abstract: The synthesized process and thermodynamic mechanisms of high-quality SiAlON dispersed phase, effect of sintering additive on the properties of composite and microstructural characterizations were investigated to obtain high performance and inexpensive SiAlON/Al₂O₃ matrix composites. Thermodynamics reactions were given in the carbothermal reduction nitridation at 1400~1700℃ which possibly occurred in the system, and finally confirmed by specific cited test(XRD). Characterizations of the microstructural observation and the resultant identified by electron diffraction pattern, would supply significant evidence for advanced composites designed and fabricated with a variety of improving mechanisms, which primarily contained suitable doping of rare metal oxide, in situ strengthening of elongated SiAlON grain and high bonding of interfacial layer.