A series of swelling tests is performed on a typical Nanyang expansive soil with medium swelling capacity compacted at various initial densities and water contents. The swelling tests are separately conducted using the conventional oedometer to confine the lateral swelling of the soil specimens, and using the GDS triaxial apparatus to allow the free volumetric swelling. The multiple nonlinear mathematical method is adopted to obtain the lateral swelling model (i.e. K0 model ), which fully considers the coupled effect of initial degree of compaction, moisture content and overburden pressure on the swelling strain. Also, an empirical model for the relationship between spherical stress and volumetric strain is proposed by triaxial swelling test. Based on the K0 swelling model, a formula is proposed to quantitatively evaluate the swell potential, and also a theoretical calculation method is derived to determine the processing layer thickness of expansive soil slope. Based on the assumption that volumetric swelling strain only changes with spherical stress and is not affected by the deviatoric stress, the correlations between the K0 model and triaxial model are analyzed, and a method to calculate the volumetric swelling strain by only employing the K0 model is given. Experimental results show that the proposed K0 model with multifactor coupling is reasonable to predict the swelling potential of compacted expansive soil. It is found that the key factor to link the K0 model and triaxial swelling model is assuming an average static lateral pressure coefficient. The average static lateral pressure coefficient tends to decreases with increasing overburden pressure by inversion method. This tendency of average static lateral pressure coefficient is believed to rely on the fact that lateral swelling pressure decreases with the increase of overburden pressure.