With the three-site Hubbard model and Floquet theorem, we investigate the dynamic behaviours of an exciton confined in three-quantum-dots molecules driven by an alternating current electrical field. The calculations show that the initia l localized state is hold up for a certain value of strength and frequency of th e alternating current field. In order to understand the dynamical property, we a pply the perturbation theory to solve the Floquet function and obtain the analyt ical solution of quasi-energy. We find that the dynamical localization can be bu ilt at the crossing point of quasi-energies for strong and moderate fields.