Abstract: Expansive soil is a special clay with remarkable shrink-swell,many cracks,and repeated deformation. It is very sensitive to the change of the external environment,which causes deformation and stability to gradually become the main subject of engineering construction in expansive soil area. This paper summarizes and analyzes the existing expansion models. It is based on the regularity that the swelling deformation of expansive soil increases with the increase of initial dry density and decreases with the increase of initial water content and vertical pressure. It proposes a loading expansion model under multi-factor coupling. In this model,the influence of initial dry density is reflected by degree of compaction. When controlled as a single factor variable,there is a linear relationship between the swelling rate and the degree of compaction,and a logarithmic relationship with the initial moisture content and vertical pressure. The loading expansion test results of strong expansive soil in Handan,medium expansive soil in Nanyang and weak expansive soil in Ninghuai are verified. All the fitting results are better. The engineering application of the model is discussed,including the estimation of the treatment thickness in expansive soil area,and the design and calculation of the lining thickness of the expansive soil slope.