The utility model discloses a system for identifying the damage to bridge structural stiffness and belongs to the technical field of bridge structural engineering. The system comprises an external load applying device and displacement meters; the external load applying device is disposed at a force bearing part of a bridge; the displacement meters are installed in pairs at the lower edge of a caring cross section of the force bearing part of the bridge; the number of the displacement meters on each bridge is at least eight pairs; and the external load applying device is a jack. Compared with the prior art, the system for identifying the damage to the bridge structural stiffness is simple to operate, accurate and reliable in result, easy for engineering and technical staff to grasp, and suitable for quality evaluation in the bridge and structure construction and operation process or rapid detection and assessment when damage or deterioration occurs.