This article deals with the favorable influence of earthworm on soil structure formation. Investigation revealed that most of the smoothly egg-shaped, elliptic or round aggregates in sail were the products of the life activities of earthworm. Electron microscopic study showed that earthworm played an important part in the formation of organo-mineral complez in soil. Therefore, the aggregates formed by earthworms possessed a higher water-stability and the ability of nutrient supply and retentibn. It is assumed that there is possibility of using the earthworm activity as a means for the improvement of soil fertility.