Abstract: Based on the orthogonal and order orthogonal decomposition of a function and interval mathematics, obtain the interval expanded order system method. In this paper, analyze the static response of structure with uncertain parameters by use of the expanded order system equation. An uncertainty parameter is treated as a bounded interval. Based on the finite element model and linear representation of a mechanics matrix of an uncertain structure, taking the advantage of an extended order system method, obtain the static responses of a structure with interval parameters. Finally using a numerical example, we compare the results with the exact ones, and then we discuss the influence of the order of expansion and uncertainty. The results show that the feasibility and effectiveness of the interval extended order system method.