Abstract: The thermal fields and thermal expansion are used to simulate the moisture fields and swelling of expansive soils upon wetting in this study. The thermal-mechanical coupled finite element analysis is employed to simulate the "expansive soil-EPS inclusion-retaining wall" system using ABAQUS. The following influences are analyzed: (1) the interface friction among the EPS, the wall and the expansive soil; (2) the width of the expansive soil, and (3) the gap between the EPS blocks. The numerical results indicate that the lateral pressure on the retaining wall increases as the width of the expansive soil increases until the width exceeds two times the height of the retaining wall. The interface friction induces redistribution of the lateral pressure on the wall and affects of the overturning moment on the wall. The gaps between the EPS blocks do not affect the lateral pressure on the wall. The interaction mechanisms between expansive soil, EPS inclusion and retaining wall are explored based on the numerical results, and a model for calculating the lateral pressure on the "expansive soil-EPS inclusion-retaining wall" is proposed. The design method for the "expansive soil-EPS inclusion-retaining wall" is illustrated by taking the gravity retaining wall as an example.