A series of prototype tests on the stability of a person in a flow are carried out in a large current basin to investigate the experiments, current force on the men's body was measured, and falling of man was observed. The major conclusions are as follows: results on the relationship between soil reaction p and pile deflection y show that Kubo's formula (p∞y0.5) is applicable to more than 15 cm of under virgin loading conditions. 2) the deflections and inclination angles of the pile increase with the loading cycles and increasing ratios have linear relations to logarithmic number of loading cycle while the magnitude of the load is kept constant. 3) the method for estimating the pile behavior under large deflection and repeated loads is presented.