Abstract: Suction penetration and ultimate uplift capacity are the two keyissues in the design and construction of suction caissons used as suction anchorsin deep water or multi-caisson foundations for the offshore platforms/windturbines. A programme of large-scale model tests on a suction caisson iscarried out in a large soil tank in Zhejiang University to study the behaviors of the caisson foundations during suction penetration and pullout. The test results of suction penetration show that the suction under the lid just has aslight influence on installation resistance of the caissons in silt, and the suction required to penetrate the caisson without soil piping is well predicted based on the results of CPT tests. The pullout tests with different loading rates are also carried out, and the results indicate that loading rate has little effect on the performance of the caisson foundation if a critical loading rate is surpassed. Based on the test results, the ultimate pullout capacitiesof the caissons in silt for different loading conditions are presented.