In order to investigate the effect of curing period and cement content of the specimen on fracture toughness of cement treated aggregate, a series of parametric tests have been conducted. By means of three-point bending method, the fracture toughness of cement treated aggregate was measured. In this study, four specimen curing periods (14 d, 28 d, 60 d and 90 d) and four different cement contents (4%, 5%, 6% and 7%) were used. The results indicate that the fracture toughness of cement treated aggregate is increasing with the increase of specimen curing period. Besides, with the increase of cement content, there is a tendency to decrease in the fracture toughness of cement treated aggregate. The higher cement content will be adverse to prevent the fine fissure inside cement treated aggregate base layer spreading further.