Abstract: To improve the calculation accuracy of the Swedish slice method, the interaction forces are usually to be considered. Based on the physical nature, this paper proposes the partial and whole hydraulic pressure methods to analyze the stability of the saturated underwater slope. These methods are used to discriminate two conflicting formulas in the Swedish slice method. It is pointed out that one formula has a lower accuracy because the vertical components of the soil slice's top surface and the bottom water pressure are directly taken to build the equations of equilibrium, and the impact of the horizontal components is ignored. It is also pointed out that these two methods can be universally used to improve the calculation accuracy of the analysis of the saturated slope.