The mechanical properties and microstructure of different content of Titanium nitride (TiN) particulates added Aluminum oxynitride (AlON) ceramic composites were studied by using DSC, SEM, TEM, XRD techniques. AlON and TiN were the only main phases in this dense material. No reaction was noticed between the AlON matrix and TiN particles. The TiN particles can delay the decompostion temperature of AlON s. The mechanical properties increases with an increasing TiN content. The extensive microcracking commonly existing around the very large TiN grains, due to the high thermal expansion mismatch between AlON and TiN, was considered to have brought about positive effects on the strength of the composites materials and on toughening. The mechanical properties increases with an increasing sintering temperature, due to compactness of the composites, then degraded because of enormous grain growth of AlON and TiN. Finally, possible processes were discussed for the improvement of the properties of AlON-TiN composites.