Currently, the factor method is usually used to grade agriculture land, however, the modification method, as an important means, is rarely used. Based on Yixing as a case study, processes of agricultural land gradation using the modification method, including technical route, partition of index control section and gradation units, selection and quantification of factors to be modified, computation of gradation index values, grading and improvement, were discussed. Comparison with the factor method was also done. Results indicate that the modification method is consistent with the factor method in terms of principle, but the modification method is based on results of agriculture land classification, making them more detailed and smaller in units. As a result, the modification method can not only save workload but also make results of the land gradation more comparable transversely.