Abstract: The development of structural system identification without input information in recent years is reviewed and the characteristics of some proposed algorithms for both input and system identification are summarized.Combined with the features of the Statistical Average Algorithm,a new iterative procedure based on the least-square criterion is put forward for structural multiple inversion.This method can be applied to the situation when multi-loads acting on the structure are unknown.Compared with other approaches for solving only one unknown input,this method has a wider application background.A four story shear building,as the numerical example,is given for verifying this method.The identification results through the noise free measurements and the noise included measurements show the applicability of this method.