Abstract: The landslide of expansive soil slope has the characteristics of long-term and recurrence, so the long-term stability of canal slope after reinforcement is still worthy of attention. In a long distance water diversion project, although the replacement measure for surface soil was adopted, the water vapor exchange between the expansive soil and the external environment was not completely blocked. After two years of operation, obvious deformation occurred, and then measures of the umbrella anchor reinforcement and drainage hole layout were taken. Based on the monitoring data of the reinforced canal slope, the temporal and spatial deformation characteristics were analyzed by the HCPC method (hierarchical cluster analysis on principal component analysis). On this basis, the typical point was selected, the exponential smoothing method, the autoregressive moving average model and the multi factor nonlinear regression model were applied to analyze and predict the slope deformation. The results show that the deformation of the reinforced canal slope tended to be stable after nearly two months of adjustment, and was mainly affected by the external environment factors and fluctuated slightly at this stage. The deformation of the reinforced canal slope was inhomogenous in space, and the deformation range decreased to both sides with the original deformation body as the center. The canal slope deformation is mainly affected by time dependent effect, as well as rainfall, groundwater level and temperature. In view of the long-term repeated characteristics of expansive soil landslide, the follow-up observation should be strengthened.