A structural damage identification method based on quadratic covariance matrix parameters of random vibration response is proposed.Firstly,it is proved that the quadratic covariance matrix parameters of the dynamic strain of the structure under the random excitation of white noise are functions of the structural modal parameters(such as frequency,mode shape,etc.),and the damage of the structure will cause the change of the quadratic covariance matrix parameters.Then,through the finite element numerical simulation and test of the simply supported steel beam,and using the parameter vector change...