Soil fertility was an important component of soil quality. In order to investigate the present statue of sloping farmland soil fertility in the water erosion zone of China, selecting field scale as the research unit, soil samples from the soil layer of 0—20 cm were collected and tested 11 soil physical and chemical indicators for 36 sampling sites. The principal component analysis (PCA) combined with Norm values and correlation coefficients between the 11 indicators were employed to select the key indexes for representing soil quality. The key indexes were soil organic matter, total kalium, pH value, cation exchange capacity and clay content. S-type and parabola-type membership functions were used to transform the indicators into dimensionless dates and to evaluate single indicators. Comprehensive index model was used to calculate integrated fertility index (IFI) for each sampling point, providing the basis for quantitative analysis of sloping farmland soil fertility in the water erosion zone of China. The results showed that: (1)The values of membership functions of the indexes revealed the CEC and clay were the major limiting factors for this region. (2)The IFI for water erosion zone of China varied from 0.17 to 0.72, and the mean value was 0.44±0.15, belonging to moderate fertility level. The proportions of integrated fertility index ranked a slow, middle, high level were 27.8%, 58.3% and 13.9% of the total area of sloping farmland, respectively. (3)There was no significant difference about integrated fertility indexes between the six secondary partition regions. The IFI of the northeast low mountain and rolling hill region was the highest, while the IFI of the Loess plateau region was the lowest. The results of the study had guiding significance for rational fertilization and sustainable utilization of land resources for sloping farmland in the water erosion zone of China.