Abstract: An approach to determine the pile behaviors was proposed based on the O-cell test results of piles,including the fundamental method,steps and necessary data.For example,the resistance parameters of piles,the load-settlement curves and the ultimate bearing capacity of piles of a highway bridge were determined by use of the proposed approach.It was validated that the relationship between the side resistance of piles and the difference of tangential displacement between two sides of the pile-soil interface could be expressed by hyperbola.The obtained load-settlement curves were compared with those obtained from other four methods,and the reliability and suitability of these methods to determine load-settlement curves of pile based on the O-cell test results were assessed.In addition,the ultimate bearing capacity obtained from the load-settlement curves was compared with that obtained from the popular formulas,and it was pointed out that the ultimate bearing capacity of piles was underestimated by the popular formulas,and a proposal to modify the popular formulas was presented.It was emphasized that the bearing capacity of piles could be determined reliably based on the O-cell test results of piles only when the perfect load-settlement curves of pile was determined appropriately by reasonable methods.