Abstract: A series of horizontal cyclic loading（resulted from wind and waves in deep sea）model tests on modified suction caissons（MSCs）are conducted under variable amplitude and asymmetrical cyclic loads. The factors concerned with cumulative displacement and rotation,such as amplitude,number of cycles,cyclic order,asymmetry（two-way）are discussed. The results show that the cumulative displacement and rotation of MSCs with a small amplitude increment and number of cycles（Δζ_b=0.1,N=500）are greater than that with a larger amplitude increment and number of cycles（Δζ_b=0.2,N=1000）under progressively increased cyclic loading; under asymmetric loading（ ζ_c=-0.3）,the cumulative displacement and rotation of MSCs tend to increase compared with that under symmetric loading;under fully two-way loading（ ζ_c=-1.0）,the cumulative displacement and rotation of MSCs decrease by 1/3 compared with that under unidirectional cyclic loading after changing the direction. The cumulative displacement and rotation of MSCs are 50% of regular suction caissons（RSCs）under variable amplitude and asymmetrical cyclic loading.