The macroscopic mechanical response and micro-fracture mechanism of Al2O3/SiC composite as a multiphase ceramic under impact loading were investigated. The dynamic strength and strain rate sensitivity were analyzed by load tests methods of one-dimensional stress wave and plane shock wave. The Hugoniot curve of high pressure and local deformation characteristics of material were determined at different stress modes. The results show that the micro-fracture mechanism of the multiphase ceramic differs with the macro-stress characteristics. The macro-deformation of the multiphase ceramic is mainly a brittle failure under impact loading. However, there are some local plastic deformation characteristics on the transcrystalline fracture of large grain and the intergranular fracture of small grain. The SiC particles as a second phase induce crack propagation at grain boundaries and within grains, which plays an important role in the redistribution of impact energy.