Strengthening the embankments on soft foundations is generally capable of improving stability. Based on this understanding, for soil foundations whose stability does not meet specification requirements, embankments are strengthened during design to improve the overall stability of the foundation. However, the actual increase is limited. In particular, for soft foundations, increase in the strength of the embankment is high will damage the foundation. Thus, the use of high-strength geotextiles is common in this situation. This study considers that the safety factor, which is usually determined using the overall stability analysis method, may feature a high level of risk. When the strength of the embankment differs considerably from the strength of the soft foundation, the safety factor of soft foundation embankment may be less than the overall stability safety factor. Therefore, to calculate the stability of soft soil foundation embankment, in addition to the overall stability calculation, the stability of the soft foundation should be reviewed. This study illustrates the correctness of this point of view. A method for calculating the stability of soft foundation is proposed. Based on this method, a calculation method for the overall stability of the embankment under scouring condition is proposed. Based on the original foundation bearing capacity model, the method considers the difference between the dike foundation and rigid foundation. Variable elasticity width fully reflects the most likely point of foundation failure occurrence when the dike is damaged. The stability of the foundation is increased by increasing the accuracy of the slip zone. Based on this method, this study also discusses the stability of the foundation under the scouring of the embankment. This method can provide a more reasonable and reliable design calculation for the safety of embankments on soft foundations.