Abstract: Based on the existing composite foundation engineering examples of a coal bunker, field testing and subsidence monitoring, combined with the FLAC^3D numerical simulation method, we studied the subsidence deformation characteristics of coal bunker buildings under variable load.The results showed that with the change of coal storage capacity, the composite foundation deformation curve changed in a wave shape, that is, the load increased, the foundation subsidence occurred, the load decreased, the subsidence deformation gradually recovered, and finally the residual deformation occurred.Under each cycle of loading-unloading, the composite foundation subsidence deformation and residual deformation have a tendency to increase from the center to the edge; The amount of residual deformation of the foundation is affected by the size of the load and the time of action.The greater the load, the greater the residual deformation of the foundation; The residual deformation increases with the increase of the cycle period of load, resulting in the continual enlarge of differences of the foundation center and edge area's subsidence.