Based on analysis of the purpose of the practice of grading and rating of agricultural land, the process of grading and rating of agricultural land was decomposed as gradation, rating of the realistic grade and rating of the potential grade and connotations of the gradation, realistic grade and potential grade, principles for selection of factors of evaluation were defined. Gradation was considered as a special quality index of agricultural land under the condition of growing population with limited land resources; rating of the realistic grade an important index of the earning ability of the land under farming; rating of the potential grade an important index of the potential earning ability of the land to be used for construction. The close relationship between the price of servitude and the price of ownership of the realistic grade and potential grade of agricultural land, which was the basic theory for evaluation of agricultural land. At the same time, the relationship between the gradation, rating and evaluation and the academic and practical significance of defining gradation, realistic grade and potential grade were elaborated.