Abstract: Two dwelling buildings with 18 stores are proposed on a ground consisting of,soft marine clay. The foundation is treated with vibroflotation. Based on the comparison of the load tests and the settlement curves, it is founded that the modulus on initial linear part of the curve of load tests does not truly express the compression of the composite ground for the raft-foundation and that the settlement is related with later linear part of the curve of load tests This article is about the calculation method of the deformation modulus of two layers composite ground within the plate influence from the data of load-test. It is close that the calculation settlement with the modulus compared with the calculation settlement with the measured settlement of the two buildings. The two layers modulus from load-test is avoid of the defect of the using method which only one layer modulus of deformation is gained.