During the course of stress calculation, the concrete watertight wall and the soil around are supposed to be linear elastic material, the onsolidation of dam is supposed to be completed before the watertight wall is constructed, the contact element is adopted to simulate the interface between the dam and watertight wall, and the completed before the watertight wall is constructed, the contact element is adopted to simulate the interface between the dam and watertight wall, and the influence towards the stress of watertight wall when water elevation changes is calculated by fem 应力计算时将砼防渗墙及周围土体假设成线弹性材料,假设在防渗墙施工时坝体固结已经完成,用接触单元模拟坝体和防渗墙之间的接触面,利用有限元计算出水位变化对防渗墙应力的影响。