The realistic structural systems are usually differs from computational model to large extent because of various undetermined causes.In this paper the so-called regularized structural stiffness parameters and damping parameters are constructed for the problems of damage identification without any structural parameters and base input information.The nonlinear least square iteration optimization method with respect to the regularized system parameters and inter-stories mass ratio is proposed.The formula for damage identification and base input inversion in terms of regularized parameters are derived.Numerical examples indicate that the method is reliable.Therefore

this new method can be applied to the practical engineering.