One of the agricultural extension method, Farmers Field School （FFS） is now considered really effective to promote social forestry project after the success of Intensified Social Forestry Project （ISFP） in semi-arid areas of Kenya. This research aimed to find out the reason why FFS method can lead participants to actively conduct social forestry activities after FFS graduation by utilizing environment-conscious behaviors model. As a result, it is found that activeness of social forestry activities can be explained by hypothetical tree-planting behaviors model and also FFS method developed some psychological indicator thorough well-considered long term learning curriculum.