Abstract: Rainfall is one of the main factors which trigger landslide of expansive soil. In order to study the landslide mechanism of expansive soil slope, a rainfall simulation used in centrifugal model tests is designed. The landslide process of expansive soil slope under rainfall is simulated by centrifugal model tests. The results indicate that the landslide appears after the first rainfall, and the scale and depth of landslide after the second rainfall increase which reflects the progressive and gradually tractional landslide of expansive soil. Finally, through the summary analysis based on the test results, the landslide mechanism of expansive soil slope under rainfall is obtained. The failure mode of expansive soil slope is proposed, that is, ‘slope slide under expansive effect’.