Abstract: Taking a 25 m-high expansive soil temporary channel slope as the research object, through the field channel tests on sliding channel slope, long and large cracks are found at the left and right banks of the channel in the elevation between 140~142 m, and the slope instability is under the control of crack strength. According to the position and shape of the slip surface, a representative channel section is selected to carry out the design of the prestressed umbrella anchor reinforcement scheme, and a complete monitoring section with anchor force and deformation as the main monitoring means is arranged. Aiming at the low accuracy of the existing soil slope anchor force monitoring, an indoor physical model test is carried out to study the applicability of the prestressed umbrella anchors for soil slope monitoring. According to the results of the in-situ monitoring and model tests, the stable states of the canal slope during the processes of excavation, reinforcement and rainfall are analyzed. The key factors affecting the stability of the canal slope and the rationality of the canal slope reinforcement scheme are clarified. The criterion for stability state judgment of high expansive soil slopes are put forward based on the anchor force monitoring.