Based on the PDA test on the 70～76 m long steel tube piles driven into Yangpu harbor of Hainan province, we probe into the behavior of the super-long steel tube pile in deep clay and draw conclusions as follows: 1) The super-long steel tube pile in deep clay area behaviors like the friction pile, and the friction resistance is over 80% of the ultimate bearing capacity; 2) The tip resistance of super-long steel tube pile in deep clay the can be fully functional, and the plugged effect of the pile tip is about 0.83; 3) The energy transfer coefficient of super-long steel tube pile in deep clay is about 0.30. Furthermore, the behavior of super-long steel tube piles is discussed with respect to their contribution to the bearing capacity in deep clay area.