Abstract: Farmland classification and gradation is to scientifically quantify the quantity, quality and distribution of farmland through quantitative indicators, and to comprehensively assess and classify the quality of farmland. It is an effective measure to realize the balance of cultivated land occupation and compensation and to ensure the dynamic balance of total cultivated land. The core of farmland classification is the nationally comparable index calculating and hierarchical system establishing. Productive ratio coefficient is the important parameter that directly affects the results of farmland classification and national comparability in the process of calculating grading index. The function of productive ratio coefficient is to convert grain into standard grain to achieve national comparability. However, the basis of determining the productive ratio coefficient in different regions is different, and the grading results cannot reach the national comparability. Nutrition equivalent unit, calculated by the mean of nutrient density in food, can reflect the overall condition of the nutrients contained in the food. It is an evaluation index to measure the total content of different nutrients in food according to the types and contents of nutrients in food, and to evaluate the comprehensive nutrients supply ability of food needed by the body. By comparing the nutrition equivalent unit of different foods, we can make a comprehensive evaluation and judgment on the nutritional value of different foods. Considering that though base crops and designated crops are different in different regions, they can be uniformly and comparable at the level of nutrients required by crops to supply energy and nutrients to human body. Based on this, 20 nutrient indices, such as protein, fat, carbohydrate, mineral and vitamin, and nine crops regulated by standard tillage system were selected to construct a nutrient equivalent correction method. Productive ratio coefficient was revised by calculating the "nutrition equivalent unit" of different crops to improve the national comparability of farmland classification results. Taking land consolidation project area in Quzhou county of Hebei Province with wheat as the base crop in northern China and Dingshu town, Yixing City, Jiangsu Province, with rice as the base crop in southern China as examples to carry out research, the productive ratio coefficient was calculated by the nutrient equivalent correction method and the max yield ratio method, and in this paper, we compared the differences of farmland nature grade obtained by two methods. The results showed that the natural quality index range of Quzhou County's land consolidation project area increased from 2 060-2 896 to 2 516-3 580, and the nature grade increased from 11-15 to 13-18. The natural quality index range of Dingshu town decreased from 2 460-2 918 to 2 033-2 393, and the nature grade decreased from 13-15 to 11-12. The natural grade difference of farmland between two research areas expanded. By revising the existing productive ratio coefficient and establishing a more standardized grading system, this paper provides a scientific basis for ascertaining the quality of resources and for the balance of cultivated land in different places. It is an important way and means for deepening both the quantity of farmland resources and the quality of the management.