The breakwater with multi-compartment single-bucket structure is a new type of structure applied in soft foundations. To explore the stress characteristics of multi-compartment single-bucket structure breakwater under horizontal loading is of great importance in its stability analysis. In this study, quasi-static force is adopted to analyze the motion mode and the earth pressure development acting on the structure as horizontal load increases. The results show that the structure rotates around a point below its foundation base under the acting of horizontal force. The rotation center moves to the axis position of the structure when reaching limit state. Meanwhile, earth pressures on the foundation bucket can be divided into active pressure, passive pressure and static pressure. On the basis of above conclusions, the limit equilibrium method is derived to analyze its stability. In addition, comparison of the anti-overturning safety factor between critical equilibrium method and finite element calculation shows that the difference between two data sets is about 20%~25%, because of their different assumptions. Theoretical results are larger and the parametric changing tendency in limit equilibrium method agrees well with that of numerical simulation, which provides some reference data for theoretical design system of breakwater with multi-compartment single-bucket structure.