Under a scouring action, scouring holes occur around a suction bucket foundation and have different depths and widths. The loss of soil in scouring holes causes changes in the stress history of the remaining soil. In this study, considering the stress history, scouring depth, scouring width, and length-diameter ratio, we conducted a horizontal static loading model test of a suction bucket foundation in sand. We obtained a variation law for the ultimate bearing capacity of the foundation considering three aspects: displacement change, soil pressure distribution, and turning point position. In addition, we summarized the relationship between horizontal loads and displacements at different aspect ratios. We also demonstrated the influence of scouring factors on the distribution of soil pressure and the rotation point and revealed the mechanism influencing the scouring depth, scouring width, and history of stress on the horizontal bearing capacity of a suction bucket foundation.