Directionally solidified Alumina-based eutectic ceramic in situ composite is a kind of promising candidate for high temperature structural material applied at elevated temperature above 1923K because of its excellent properties. With laser zone melting directional solidification, Al2O3/Y3Al5O12 (YAG) eutectic ceramics are successfully prepared. The relationship between the eutectic microstructure and the processing parameter is studied, and the mechanical property of the composite is measured. The results show that: (1) Laser power density and scanning rate strongly affect the eutectic microstructure. With proper processing parameters adjusted, the binary lamellar eutectic microstructure is obtained, in which Al2O3 and YAG phases are three-dimensionally coupled and continuously connected without grain boundaries and amorphous interface phases. (2) The eutectic spacing decreases to about 1μm with increasing scanning rate. (3) The maximum hardness of 19.5GPa and the room fracture toughness of 3.6MPa.m1/2 are obtained by Vickers indentation measurement.