The interaction of atomic clusters with high-intensity lasers has been investigated based on the hydrodynamic model developed by Ditmire et al.By solving Maxwell equations,an effective plasma dielectric constant is found to replace the quasistatic plasma dielectric constant ε derived from the Drude model.In the vicinity of resonance absorption,the electron density and temperature undergo such a rapid change that the quasistatic plasma dielectric constant ε is no longer appropriate to demonstrate the behavior of resonance absorption.Employing this model,the interaction of atomic clusters with high-intensity lasers at different frequencies has also been studied.