Mullite is one of the most important ceramics that show high thermal shock resistance. However the application of mullite is limited by low sinterability, formation at high temperature and low ductility. One of the methods for improving mechanical property of mullite is to add a secondary phase. Magnesium aluminate spinel is one of the oxide ceramics that with its unique properties such as high mechanical strength, it can be used to strengthen the mullite phase. The need for high temperatures to form both the mullite and spinel phases is another factor in the production path of both phases. So the purpose of this study was synthesis and characterization of mullite-magnesium aluminate spinel composite by mechanical activation and review the optimal production conditions. The material used in this study was activated alumina and talc. As received materials were mixed according to stoichiometric ratio and then heat treated to form mullite-magnesium aluminate spinel composite. The effect of activation time, heat treatment temperature and using of industrial talc on the phase transformation and crystallite size of the composite were investigated. Various techniques were employed to evaluate and characterize the produced product. To evaluate the phase structure and support of appearance of desirable phases in obtained composition, X- ray diffraction (XRD) technique was used. Thermal gravimetry analysis (TGA) was used to evaluate the thermal behavior of produced product. To investigate the morphology and particle size distribution of starting and obtained powders, scanning electron microscopy (SEM) was employed. Also, morphology and crystallite size nanocrystalline composite powders were characterized by transition electron microscopy (TEM). Energy dispersive X-ray (EDX) was used to detect the elemental change in different phases. The result showed that lack of purity in raw materials causing delayed the formation of the mullite at higher temperatures and the formation of forsterite in the structure. Also the result showed that by changing the mechanical activation parameters including increasing the bulled to weight ratio, using different sized pellets and increasing the rolling speed of the mill, the mechanical activation time can de decreased from 100 h to 10 h. The mullite magnesium aluminate spinel nanocomposite was successfully synthesized with a crystallite size of mullite 30 nm and spinel 20 nm after 10h of mechanical activation and 3h heat treatment of activated alumina and pure talc at 1300 °C. ,