Relationship between K_2O-Al_2O_3-SiO_2 system dental glass ceramics and Al_2O_3 ceramics was investigated. 4 groups of glass ceramic with the same components but different thickness(0.8, 1.2, 1.6, and 2.0 mm) were sintered on Al_2O_3 base ceramics according to the same thermal treatment system of leucite micro-crystallization reported in previous literatures. The products of each group were analyzed by polarizing microscope, X-ray diffractometer, and an INSTRON material testing machine. Under the thermal treatment system, leucite crystals were formed in samples of each group, and dispersed evenly. Meanwhile, the compressive strengths of group 3 and group 4 were higher than those of group 1 and group 2. Samples of group 3 showed better mechanical properties than others. The conclusions are drawn that Leucite crystals can be controlled in K_2O-Al_2O_3-SiO_2 system glass ceramic-Al_2O_3 ceramic composite material, and the thickness of glass ceramic has a notable influence on the compressive strength of this ceramic composite material. 4 groups of glass ceramic with the same components but different thickness (0.8, 1.2, 1.6, and 2.0 mm) were sintered on Al_2O_3 base ceramics according to the same thermal treatment system of leucite micro-crystallization reported in previous literatures. The products of each group were analyzed by polarizing microscope, X-ray diffractometer, and an INSTRON material testing machine. Under the thermal treatment system, leucite crystals were formed in samples of each group, and dispersed evenly. Meanwhile, the compressive strengths of group 3 and group 4 were higher than those of group 1 and group 2. Samples of group 3 showed better mechanical properties than others. The conclusions are drawn that Leucite crystals can be controlled in K_2O-Al_2O_3-SiO_2 system glass ceramic-Al_2O_3 ceramic composite material, and the thickness of glass ceramic has a not can influence on the compress ive strength of this ceramic composite material.