Abstract: The modified suction caisson (MSC) has the advantages of high bearing capacity and ability to control lateral deflection, which is very suitable as a foundation for ultra-large offshore wind turbines. The wind and wave loads acting on offshore wind turbine structures have misalignment behavior, resulting in extremely complex foundation bearing characteristics. Model tests were carried out to study the responses of the accumulative lateral deflection, motion law and horizontal bearing capacity of the MSC in sand to misalignment monotonic (simulated wind load) and cyclic loadings (simulated wave load). Results show that under coplanar loading, the motion direction of the MSC is always consistent with the direction of load. However, under misalignment loading, the MSC gradually moves to the monotonic load direction in the horizontal plane, and this phenomenon gradually becomes obvious with the increase of the cyclic load amplitude and the degree of bidirectional cyclic loading. Under the same loading cycles, the maximum total accumulative lateral deflection of the MSC occurs when the angle between the monotonic load and the cyclic load is 30°. Under each load angle, the total accumulative lateral deflection of the MSC is smaller than that of the regular suction caisson. Based on the experimental results, the prediction formula of the total accumulative lateral deflection in the horizontal plane of the MSC under the combined action of misalignment monotonic and cyclic load is obtained. In addition, the horizontal bearing capacity of the MSC after misalignment loading increases with that prior to misalignment loading. The reason is that the sand around the foundation becomes compacted due to cyclic loading. However, after misalignment loading, the bearing capacity of the MSC is lower than thatunder the coplanar loading, and the reduction value gradually increases with the increase of the angle between the monotonic load and the cyclic load. The research results provide a reference for the application of MSC.