In soil erosion area, land productivity and farmer爷s income can be raised obviously by carrying out the measures of soil erosion control and in the meantime increasing the amount of environmental human carrying capacity. As the most important and the largest soil erosion control project in the Yangtze River, also called “Yangtze River Harness冶project, it plays an important role for improving the environment and increasing human carrying capacity. Taking the fourth stage of the project in Sichuan Province as an example, we used cluster analysis method and divided the 72 controlled watersheds into 6 groups. The environmental human carrying capacity was calculated in terms of different consumption standards (food consumption and cash consumption). The results showed that the amount of the carrying capacity had been greatly increased after control. At the same level of harness investment, the small watersheds with higher population density and grain yield per hectare have more increment of carrying capacity. Based on analyzing the typical small watersheds, the proper value of investment for the fourth stage of the project is about RMB 110 000 to 120 000 yuan per square kilometer, at the investment level of the year 1997, for the purpose of increasing environmental human carrying capacity. In comparison, the amount of rational harness investment of the first stage of the project, which is similar to that of the fourth stage, is about RMB 315 000 yuan per square kilometer at present value of 2013.