Objective To compare the fracture surface of the machinable infiltrated ceramic（MIC） prepared in different onditions, and to relate its strength and toughness to the differences in their microstructures. Methods The Al2O3 atrix were prepared, infiltrated by the machinable glass and crystallized. Based on sintering and infiltrating time and onditions, the specimens were divided into three groups: Perfect group, insufficiently infiltrated group, mal-sintered substrate roup. Specimens were fabricated, three point flexural strength and elastic modulus were tested, and the microstructure f the MIC fracture surfaces was analyzed by means of scanning electron micrograph（SEM） observation. Results he strength of the insufficiently infiltrated group and mal-sintered substrate group were lower than that of the perfect roup, and faults in the microstructure of these two groups also proved this. The foreland of glass infiltrating in the Al2O3 nd the interface of glass and complex demonstrated that the Al2O3 surface was smoother than the complex and there as a big crack in the glass but not in the complex which proved the crack resistibility of glass and Al2O3 were smaller han that of the complex（MIC）. Conclusion Correct preparing process could make the glass infiltrate into properly sintered l2O3 sufficiently which ensured best mechanical properties of the complex.
