Inhibitory processing is an emerging theme in recent psychology and cognitive sciences.To explore the mechanism and development of directed forgetting effect, totally 104 subjects from grade 2 and 5 and college participated in a directed forgetting task, in which used a blocked cuing procedure. The results indicated: (1) all age subjects demonstrated the directed forgetting effect. (2) Both retrieval inhibition and selective rehearsal played a role in directed forgetting effect, although there may be a different processing mechanism in younger children. (3) The different age groups demonstrated significant different level of inhibitory processing. The second graders showed partial inhibitory ability, the fifth graders showed better inhibitory ability, and the college students showed quite better inhibition than the fifth graders.