Reinforced concrete damage detection gain a lot of attention from researchers in last two decades. In this paper, a damage detection index have been introduced via obtained data from dynamic responses of a reinforced concrete frame. Modal shapes of healthy and damaged structure were designated as the input data for the proposed damage index. This index investigates the damage severity in different levels of frame damage through applying gradually static loading. The static loading procedure was a concentrate load at middle of the horizontal beam which arising in three levels of magnitude. The obtained results from analyzing the damage detection process show that the proposed damage index is capable in evaluating ans detecting the cracks locations and also severity in both beam and columns of the frame and consequently, it is proper to claim that the suggested index would be generally good in usage at overall damage and crack detection techniques.