Firewood collection,which reduces vegetation cover,is one of the primary reasons causing soil erosion.We studied farmers'fuel selection behavior based on field surveys as well as theoretical analyses,and found that the proportion of farmers'commercial fuel consumption has increased significantly both in terms of fuel materials and total thermal values in Changting County from 1960s to 2000s,with the latter increased faster than the former.Fuel substitution is not only a low-cost soil erosion controlling measure for government,but also a source of net income for rural households due to increases in labor opportunity cost(e.g.,farmers can make more money working in a manufactory than collecting firewood).The profit margins of using three surveyed fuel substitution schemes over the firewood decreased from"biogas & electricity" to "honeycomb briquette & electricity" to "liquefied petroleum gas( LPG) & electricity".Further theoretical analysis of comprehensive cost of firewood collection,farmers'fuel choice,and typical fuel substitution process shows that government intervention is an important factor in moving forward the fuel substitution and controlling soil erosion.