For the first time in China，the high replacement rate sand pile composite foundation is widely used in Hong Kong-Zhuhai-Macao Bridge project. The settlement deformation calculation method of the composite foundation is empirical，and the calculation results are often different. Therefore，we carry out the load test of a large composite foundation with a bearing plate side length of 5.4 m to verify the design parameters. We apply the hyperbolic model to fit the load-settlement curve of the load test，establish the relationship between the tangent modulus and the additional stress considering the nonlinear deformation of the foundation，verify the feasibility of the settlement calculation method of the tangent modulus method，and calculate and contrast the settlements of composite foundation under the main structure load by this method and the standard method respectively. The results show that the calculation result of the tangent modulus method considering the nonlinear deformation of the foundation is more consistent with the measured value.