Abstract: This paper dealed with the design of reference land unit method of arable land evaluation at county level. The core of this method WAs the calculation of arable land quality ratings by comparing the characteristics of the arable land evaluation unit and reference land unit in an area. The method was applied to evaluate the arable land at county level in Wolong district, Nanyang city, Henan province. Where the land was classified into 8 grades(grade Ⅰ to grade Ⅷ). 87.6% of the land from grade Ⅰ to grade Ⅲ distribute on alluvial and lacustrine plains. 61.4% of them from grade Ⅳ to grade Ⅵ distribute on slightly rolling parts. Grade Ⅶ and grade Ⅷ are concentrated at the foothills. The results showed that the spatial distributions of the different grades of the arable land, classified by the reference land unit method, reflected reasonably the spatial changes of geomorphological units and soil types. The linear estimation model between comparable productions and the corresponding quality ratings of 210 sample units showed that the coefficient of determination R2 is 0.876, which meant that 87.6% of the change of standart grain yield output is explained by the change of quality score of arable land. It is concluded that the arable land quality ratings calculated by the method can reflect the biologic productivities of land. Therefore, the reference land unit method designed can provide as a reference method or model for other places in China, when the arable land evaluation to be conducted.