Abstract: On the basis of one-dimensional fluid model, the characteristics of radio frequency discharge at atmospheric pressure in argon using bare metal electrode are numerically investigated. The primary processes of excitation and ionization in Ar are considered. The particles included in the model are electron, two ions Ar+ and Ar2+ and one metastable state Ar*. The spatial-temporal evolutions of the discharge density with electrode voltage and gap are calculated by solving the one-dimensional continuity and momentum equations for electrons and ions, coupled with the current continuity equation. The simulation results show that the densities of electron, Ar+, Ar2+, and ArAr* have an optimal value with the variation of electrode voltage and gap.