<p>Model tests are carried out to study the bearing characteristics of modified suction caissons (MSC) under long-term horizontal cyclic loading. The influences of the cyclic loading frequency, combination of two kinds of vertical loading and cyclic loading on the MSC horizontal displacement, cumulative rotation angle, pore water pressure inside the caisson and stiffness are obtained. The experimental results show that the horizontal displacement of MSC increases with the increase of loading frequency. Under different loading frequencies, the MSC shows an upward trend in the vertical direction, and under the same loading cycle, the upward displacement of MSC decreases with the increase of loading frequency. The maximum water pressure both inside the internal compartment and the external structure accumulates with the increase of the loading cycles. As the vertical load on the lid increases, the horizontal displacement of the MSC decreases, its overall stiffness improves, the rotation angle of the caisson is reduced, and the recovery of this rotation angle is enhanced. When the number of cycles is greater than 2000, the rotation angle of MSC increases rapidly. Under the condition of multistage cyclic loading, the stiffness of MSC gradually decreases with the increase in the number of cycles.</p>