We report the dielectric function of silver film between 1.5 eV and 3.0 eV at room temperature. Use is made of ATR (Attenuated Total Reflection) method in Kretschmann configuration in taking the measurements. And the data were checked by means of the modified free electron model. The effective mass of electrons, the modified dielectric constant of interband transition, and the electron scattering frequency were all compared with those obtained by different experiments and the theoretical calculations.