Abstract: For improving the precision of the parameter estimate,a set of pre-processing methods including filtering and normalization were proposed for the initial experimental signal according to the characteristics of the optical feedback self-mixing interference signal.The proposed approach implements filtering of noise effectively and flat the signal.The pre-processed OFSMI experimental signal tallied much with the theoretic signal.Estimating parameters using the initial and the pre-processing signal separately,comparison results show that the latter can make the accuracy of the line width spreading factorand the optical feedback level factor C improve by 5.52% and 4.55% respectively.