Linear fitting is a common problem in data processing of college physics experiments．There are two common data processing methods：successive difference method and linear regression method．The uncertainty of the result of the successive difference method and the linear regression method was evaluated bv using the Excel software．When the comparison of the two methods was carried out quantitativelv，the disadvantages of the successive difference method are obvious．So the data should be processed with the linear regression method as far as possible when making accurate measurements．The successive diffrrence method is only suitable for rough estimation of measurement results．