Abstract: The subsea mudmats are usually used to support subsea structures. When the mudmat, located on the surface of soft clayey seabed, is subjected to uplift loads, the suction force is generated at the mudmat-soil interface. The suction is beneficial in improving the stability of the mudmat, but is disadvantageous in retrieving the mudmat. Therefore, it is necessary to investigate the invert suction systematically. A series of model tests are conducted to investigate the uplift capacity of the mudmat resting on the homogeneous or lightly overconsolidated clay. The factors influencing the uplift capacity are investigated, including the uplift velocity, the soil strength, the soil heterogeneity and the degree of consolidation. Several pore pressure transducers are installed at the invert of the model mudmat to measure the generation, development, distribution and dissipation of the pore water pressure. The test results show that the uplift capacity of the mudmat is provided by the invert suction. Meanwhile, the results show that the uplift capacity and the average suction at the invert of the mudmat the increase with increasing uplift velocity, heterogeneity and degree of consolidation. In addition, it is found that the suction near the centre of the mudmat invert is greater and disappears later than that at the margin. In order to reduce the invert suction through perforating, the optimal position of perforations should be set at the centre of the mudmat.