In order to meet the requirement of improved, live load level, the method of strengthening the existing concrete suspension bridges by system transformation is presented in this paper.According to this method, the suspension system of original bridge is changed into cable-stayed-suspension system by the newly added cable and steel girder.On the basis of the strengthening done in a typical bridge,the scheme comparison and the analysis of the static behavior of the bridge before and after strengthening were performed.The results show that the bending moment of the original concrete girder is reduced obviously, and the bearing capacity of the bridge is greatly improved after strengthening.The original cable system is fully utilized and can meet the force requirement.This method has many advantages, such as greatly improved bearing capacity, best utilization of original structures and better economical benefit.It also has certain theoretical significance and practical engineering value which can be applied to a similar bridges strengthening project.