Abstract: The large scale model test proves that the rigidity of frame structure with large thick raft foundation is approximately equal to the rigidity of box foundation.When the ratio of the thickness of raft and the span of the column is bigger than 1/6,the results calculated by inverted beam method agree with that by global analysis method.Using the computation method of contact pressure and settlement acted by the local load,and then adopting the superposition principle,the settlement of the large thick raft foundation under several tall building can be obtained.