Abstract: An hyperbolic function was proposed as a load transfer function to analyze the load transfer mechanism of a single pile.By discussing the influence of various parameters on transfer function in this model,it was considered that the limit displacement among pile-soil was a main parameter in transfer function.Based on the test data of bored piles in 26 projects in Xi’an area,the parameters in load transmission function were optimized by using the optimization toolbox in Matlab,and the average values of the function parameters were obtained in every soil layer in every project.It was found that the limit displacement of pile-soil was the most dispersive parameter,which was compatible with the theoretical analysis.Finally,it was shown by the comparison between the calculated results and the actual project that it was feasible to use the average value of the optimal parameter as empirical parameter.