Abstract: It is applying strength reserve method to carry out the calculation of two-dimensional finite element for section 1+025 of main earth dam of Feilaixia in this paper, work out the horizontal displacement of characteristic point under combination about different water level upstream and downstream when the dam is at the three states of initial yielding, critical instability and unstable failure, and establish the model of the relation between horizontal displacement and upstream water level with dualistic and quadric regression method, then gain the safety monitoring index of horizontal displacement of section 1+025 in main earth dam of Feilaixia further.