Abstract: In order to improve the validity and robustness to noisy, multi-source information fusion technique is imported into structural damage identification methods. Concerning the characteristics of modal strain energy, in which whole modes should be included, information fusion technique is taken to have strain energy of every mode fused and the improved method based on modal strain energy is put forward. Through a numerical simulation of a prestressed concrete composite box beam bridge, it is revealed that this proposed method is sensitive to damage and can identify structural initial damage only with less low-order modes. At the same time, this method has good robustness to noisy. When noise intensity is less than or equal to 10%, this method can identify structural initial damage well and truly. In a word, the proposed structural damage identification method has good practicability to actual structures.