Taking the proposed offshore large cylinder project in Guangdong as an example,in view of the problem of too small displacement in the structural design based on two-dimensional theory,we use Plaxis 3D software to build a three-dimensional model of the overall space between the reinforced concrete structure and the soil,and use the HSS model in the three-dimensional finite element simulation to simulate the foundation soil and the backfill material inside the cylinder.Then we calculate the displacement of the cylinder itself and the displacement generated by the soil under different working conditions,and obtain the motion trend of the deep buried large cylinder structure,and the influence of the strength of backfill soil inside the cylinder,the thickness of the cylinder wall,and the depth of penetration on structural stability.The results show that the motion of the soil inside the cylinder and the cylindrical structure is basically the same,and there is no fully developed active and passive area.Targeted suggestions are provided for the minimum height of construction backfill.The wall thickness has a relatively small impact on structural stability,while the strength of backfill soil inside the cylinder and the depth of penetration has a significant impact on structural stability.However,after reaching a certain limit,the growth trend of stability results gradually slows down and tends to stabilize.