The distribution characteristic of contact pressure of large-area thick raft foundation under multi-tower buildings is always limited to indoor test analysis. This paper comparatively analyzes the in-situ test data from outdoor SOHO project located in Sanlitun

Beijing and the existed indoor test data. The results indicate that when the foundation soil of buildings is uniform distribution

the stiffness of upside structure is greater and the variation between intercolumniation and the load of outer column of frame is not over than 20 percentage as well as the load difference between the outer columns of frame and core-tube less than 10 percentage

when the ratio of the raft thickness to the column span is larger than 1/6

the calculation of contact pressure of raft foundation under tower buildings can be regarded as linear distribution and the load of tower buildings can be diffused by the annex foundation. The situ test in engineering practice indicates

the diffuse range of the load of tall buildings is around two spans of annex

the diffusing effect is rare over than three spans. The principle of superposition can be applied to calculate contact pressure of large-area thick raft foundation in multi-tower buildings