Abstract: In the horizontal directional drilling project of pipeline, when the backtowed pipes cross the river, the limit hydrostatic pressure caused by the fluctuation effect of water level has a vital impact on the safety of backtow. To analyze the distribution of earth stress near the bore wall and predict the stability of bore wall, proper criteria of bore wall stability is derived based on the analysis of stress field around the bore wall and the existing bore wall stability criteria. This paper adopts finite element analysis method to build a crossing model and gives a numerical analysis for the bore wall stability of model under dynamic fluctuation of the water level. The change of stress field near the bore wall is simulated under the situation that the water level continuously fluctuates after it achieves the maximum value. It is concluded that the stability of bore wall becomes poorer when the water level rises, which is of great guiding significance for the prediction and evaluation of field pipeline construction.