Damping parameters of material and structure are of great influence on structural response and damage . It is necessary to investigate the effects of steel bar on the damping behavior of reinforced concrete. On the basis of Kelvin damping model and complex damping model, the dynamical parameters analysis of material damping was carried out to obtain the theoretical reduction factor of damping capacity of the reinforced concrete when the reinforced concrete beam was on bending vibration in the elastic stage. The experimental investigation was carried out to study the relationships among loss tangent, excitation frequency and reinforcement ratio. The experimental results show that the loss tangent of material is decreased with the increasing reinforcement ratio and excitation frequency. The initial decrease is rapid, and then become smooth. In addition, the comparative analysis was done among experimental results, numerical results and theoretical reduction factor. It is found that the theoretical reduction factor is close to measured damping value when the reinforcement ratio is high. However, when the reinforcement ratio is low, there are some deviations between theoretical reduction factor and measured damping value due to ignoring the contribution of plain concrete materials.