Abstarct: Today, monopiles are the most typical foundation for offshore wind turbines. During their life-time large diameter, stiff piles are subjected to millions of small cyclic loads due to environmental forces. The long-term cyclic loading can change the granular structure of the soil surrounding the pile. This may change the resistance of the soil-pile system and lead to system failure. To estimate the displacement of the pile under axial cyclic loading, there is no universal standard method which is accepted. Therefore, to unify the study of long-term cycle loading on pile, the concept of degradation and cyclic stability diagram are adopted. In order to study the effect of physical parameters of pile, soil mechanical characteristic, stress and strain levels on soil-pile system behavior, the theories that is proposed by researchers who studied on this subject, have been used. To investigate the effect of the parameters such as length, stress level, pile diameter and soil relative density on soil-pile system behavior subjected to cyclic axial load, an efficient loading system has been installed and a series of small-scale test on galvanized piles has been performed. The soil, in which piles were embedded, was fine sand.