Abstract: In the parameter estimation,there exist two problems:changing the equivalences of the equations makes estimation results biased;determining the ridge parameter k is very difficult and random.To solve the two problems,this paper presents the iteration method by correcting characteristic value.The co-factor matrix Q_XX is derived firstly,then proves that Q_XX is just the Kaley inverse N^-1 of N in the case of rank-full,which is Moore-Penrose inverse N⁺ of N in the case of rank-defect.