Influence of tree root system on soil anti scourability improvement was studied in the bedrock coast of Zhejiang province. The results shows that root system can intensify soil anti-scourability by the action of fine roots (≤0.5 mm and 0.5～1.0 mm).The fine roots can increase soil anti scourabiliy not only by the direct consolidation of the large amount of root net, but also by the indirect improving action on soil structure after roots discomposed. The regression models of tree roots and the intensified value of soil anti-scourability had been made in this paper.