The skirt suction anchor is a new type of offshore fan foundation, which has the advantages of convenient construction and strong anti-erosion performance. Through the indoor wave flow flume erosion test, the skirt suction anchor model was installed in the flat sand bed, the wave flow condition was changed, the erosion development duration and the erosion pit shape were recorded, and the influence of different wave flow factors on the erosion development law was analyzed. When the flow velocity increases or the inundation rate decreases, the erosion range increases, the erosion development accelerates, and the erosion depth and sedimentation height increase in the quasi-equilibrium stage. The diachronic development law of scour depth around foundation under different foundation height (submergence rate) is obtained. With the increase of wave height, the maximum erosion depth first increased and then decreased, and the maximum deposition height always increased with the development of the test from the clear water erosion stage to the moving bed erosion stage. When the relative flow velocity increases, the relative erosion depth increases, and the acceleration increases first and then decreases. The scouring pit in front of the foundation is "inverted scoop", the dunes appear symmetrically on both sides of the foundation, and there are horseshoe-like silting dunes behind the foundation. When the velocity increases or the submergence rate decreases, the scale of the scour pit in front of the foundation and the silting dune in back will increase. The cylindrical skirt structure can play a good role in anti-erosion.

Based on the theory of scour protection, a multihole collar for composite foundation was designed, and the effects of collar width, thickness, and pore structure on the water flow around the foundation, the morphology of scour pits, and the time course characteristics of scour were investigated by using Flow-3D software. The results show that increasing the width of the multihole collar can reduce the strength of the horseshoe vortex in front of the pile and reduce the vortex structure near the foundation; increasing the thickness of the multihole collar can weaken the strength of the tail vortex, resulting in siltation of sediments downstream of the foundation; and the pore structure can disrupt the boundary layer of the water flow near the collar and reduce the local scour around the foundation. Among them, the thickness of the retaining collar has the most significant effect on the scour protection performance of the multihole collar, when the multihole collar thickness was increased from 2 mm to 3 mm, the maximum scour depth near the foundation was reduced by 29.08% and the start of scouring was delayed by almost 2.5 times.