Taking an expansive soil channel slope treatment projects as the research background, the variation laws of lateral stress and groundwater level of soil are investigated and the effect of slope treatment is analyzed. The monitoring results show that the variation range of groundwater level is related to the measuring point location and rainfall intensity. When the rainfall intensity is relative small, the groundwater level in the lower part of the slope varies greatly. When the rainfall intensity is high, the variation range of groundwater level in the lower part of slope is basically the same as that in the upper part. The lateral stress of soil is closely related to soil weight, expansive force and seepage force, and the lateral stress of surface soil has obvious seasonality. According to the monitoring data and numerical calculation analysis results, it is considered that cement soil replacement combined with horizontal drainage pipe has good control effect on expansive soil channel slope. The research results can provide reference for similar engineering design, construction and operation management.