Objective To investigate effects of aging on the fracture mechanical behavior of human dentin with finite element numerical method. Methods The finite element model was established according to the typical compact tension specimen in the experiment. The stable crack growth in human dentin was simulated with the cohesive zone model to compare the crack extensions of the young and aged dentin. Results The growth toughness and plateau toughness of the aged dentin were 0.51 and 1.19 MPa?m1/2, respectively, which were significantly lower than those of the young dentin (7.48, 1.71 MPa?m1/2). However, the initiation toughness of the young and aged dentin showed no significant difference with 0.51 and 0.38 MPa?m1/2, respectively. Conclusions The crack growth resistance of human dentin is decreased significantly with aging. Based on the cohesive zone model, the crack growth behavior of biological hard tissue, whose mechanical properties are related with age (such as the human dentin), can be well predicted by using numerical methods.