Abstract: A damage identification method based on cable force tests of a cable system and test error self-adaptive analysis is proposed to measure cable forces in prestressed steel structures and find out possible damage positions of the cable system. The method includes placing a laser velocimeter; measuring the vibration speed history data of the measuring point P on the cable by the laser velocimeter; calculating the cable force; calculating all the cable forces of the cable system through the same procedure; analyzing error between cables and finding out the possible damage of the cable or of the tie rod connected to the cable. The dynamic response characteristics of both in-plane and out-of-plane of a cable can be obtained through the method of the present invention. The self-verified more accurate results can be obtained, and the damage in a cable system can be determined according to error self-adaptive analysis.