The concepts of isoseismal line measurement mode and direct measurement method are added to the fitting ellipse method in the form of constraints, and the method of measuring isoseismal line based on fitting ellipses is systematically given, and the solution based on the optimization theory reduces the subjective uncertainty of the direct measurement method. The applicability and robustness of the fitting ellipse algorithm are discussed, and the results of measurement are compared with the previous results. The results show that the fitting ellipse algorithm has good applicability and is suitable for the fitting of isoseismic lines. The robustness of the fitted ellipse algorithm is good, and the results of the isoseismal line are stable, while the results of the unclosed isoseismic lines with complex shapes are relatively discrete, so it is necessary to verify whether the results are available separately. The results obtained by the fitting ellipse method are in good agreement with the previous results. In addition, the fitting ellipse method reduces the subjective uncertainty of measurement and can be used to establish the intensity attenuation relationship.