基于中国环境资源数据库及对中国耕地面积１０年变化研究的基础，采用重心模型方法，通过计算两个时期的耕地面积重心，得出中国耕地面积重心１０年向西北移动了２８．３３７７ｋｍ，尔后，在耕地生态背景质量模糊评价的基础上，生成耕地生态背景质量指数，利用此指数计算出耕地重心的移动所导致的中国耕地质量下降２．５２％的定量化数值。

According to the data base of Chinese environment resources,on the basis of the reearches on the changes of the Chinese farmland area in 10 years,the gravity centers of the farmland areas of two periods are calculated by using the method of the gravity center model. From this it is found that the gravity center of the Chinese farmland has moved 28 337 7km toward the northwest in 10 years. Then,on the basis of the fuzzy evaluation of the farmland ecological background,the quality index of the farmland ecological background is designed. By using this index the quantitative value of the decline of the Chinese farmland quality is calculated. The value is 2.52%,which is induced by the movement of the gravity center of the farmland.