AbstractThe discretization error of line in discrete global grid system is a major factor which affect the precision of discretization line and accuracy of the result of the spatial analysis. The error source of discretization of line were analysed firstly in this article. Then a experiment was designed to calculate the true length and discretization length of a line. A linear relationship was gotten by error analysis between true length and discretization length. The results of error analysis also show that the maximum and minimum relative error of discretization line were 14.52% and −10.4%.