Abstract: Based on the application background of the suction caisson foundation in bridge engineering, a numerical simulation method is used to investigate the bearing performance of the combined suction caisson foundation, and the number and spacings of caissons are considered. The effort is focused on the difference of bearing performance between the combined foundation and the single foundation, and on the contributions of connecting roofs to the bearing capacity of foundation. The analysis results show that the load-displacement curves of the combined caisson foundation are the same as those of the single caisson foundation. Similar to the pile group effect, the vertical bearing capacity of the caisson cannot be fully utilized in the combined foundation. Due to the contribution of the connecting roof between caissons, the vertical bearing capacity of the combined foundation will be greater than the sum of the corresponding numbers of the single suction foundation under a large caisson spacing, and it increases with the increasing caisson spacing. The lateral bearing capacity of the combined foundation is greater than the sum of the corresponding numbers of single suction foundation, and the contribution of connection roof can be neglected.