Abstract: Firstly, according to the interval feature of mechanical parameters for pile structures, by introducing the interval analysis theory and method and regarding mechanical parameters and response variable as interval variable s, a response surface reliability analysis mode of pile structural system based on the interval analysis probability of reliability analysis mode and reasonable function is defined by describing uncertain geotechnical mechanical parameters and the sums of calculating them. Secondly, aimed at the limitation and shortage of the interval number rules, especially when the interval variables are numerous or the range interval of functional function is quite wide, the method to determine the range interval of functional function is founded by introducing the interval-truncation approach, and it avoids the interval expansion of functional function. Finally, the proposed optimization methods is employed to compute the response surface reliability index of pile structures. The practical engineering analysis indicates that the method is of great theoretical and practical significance.