This paper studies the feasibility of using changes in dynamic properties of composite structures to detect damage. An experimental study has been carried out on steel-concrete composite beams with different shear connection systems. Three composite beams and one non-composite beam were tested for comparison. Different damage states are created using a four point load system with 20 %, 40 %, 60 %, and 80 % of the calculated ultimate loads. For each loading stage, the impact test is carried out on the beam after the static load is removed. The same tests are also conducted at initial stage and post failure stage. Dynamic responses are recorded using a data acquisition system and modal parameters are extracted using a Matlab based program. The relationship between the loading stages and changes of modal parameters is studied and it could be a good indicator of the damage in the steel-concrete composite structure.