Taking Changting County of Fujian Province as a study area, based on the geomatics technology, the amount of soil and water loss was calculated by using USLE(universal soil loss equation). Then combined with the green biomass of every town, the model of quantitative description of the relationship between these two factors was established. The result showed that the green biomass of unit area was negative correlated to soil and water loss obviously, the R² of each model was more than 0.5. The research conclusion can provide support for decision-making of regional forest management and soil and water conservation.