Abstract: When violent break-up occurs in a natural river course, it is easy to produce ice jam and ice dam to cause the flood disaster. Based on the analysis of the ice-breaking water level and the measured daily water level, it is an important non-engineering measure to forecast the river opening mode and opening date in advance and adopt the corresponding prevention technology in time. In this study, based on the theory of ice sheet deflection damage, the water level change is used to judge the river opening pattern, the degree-day method of the one-dimensional ice thickness model is optimized, the change of ice thickness in the river channel is calculated, and the river opening mode and date of Heilong River in 2015-2018 is forecasted. The results show that except for the error of one day between the predicted value and the measured value in 2017, the predicted value and the measured value in the other years are identical for the ice break-up date, except that the insufficient hydrodynamics caused by the low water level in 2018, which affects the accuracy of the prediction, the predicted value and the measured value in the other years are identical for the ice break-up mode.