A long term soil conservation site set up on sloping farmland in Luodian county of Guizhou province for studying on changes of crop yield and soil fertility in several soil conservation measures. The results in 9 years showed that runoff and soil erosion was the main factor in affecting the degradation of soil fertility and nutrient loss on sloping farmland. Treatment without erosion control the nutrients loss by runoff and soil erosion on sloping farmland was 53.0 % of total nitrogen, 67.7% of total phosphorous and 19.0 % of available potassium, comparison with the total consumption of those soil nutrients, or almost equaled to the total N input of chemical fertilizer, total P input on both organic and inorganic fertilizers. Soil organic matter loss was nearly same with the input of organic manure. Total N, organic matter and available K in the treatment soils decreased,and total P is kept in lower level by the heave nutrient erosion. Treatments with water and soil conservation the soil fertility kept balance or even increased in soils. For alley cropping treatment corn yield increased 8.6 % in average of nine years and trend to increasing forward. The long term experiment showed that proper soil conservation technology would improve soil fertility, increase crop yield and play an important role for sustainable use of the sloping farmland.