Abstract: Rainfall, especially in rainstorm conditions, is one of the major factors considered in simulating landslides. Landslides often occur on the southern slope of Washan stope in Nanshan iron mine as the slope has increased in height and steepness. To determine the influence of rainfall on slope stability, the southern slope of Washan stope was monitored dynamically by MSR300 radar system for four years in real time. Based on data on rainfall and slope deformation, the slope deformation law between rainfall and rainfall intensity was analyzed. The stages of a landslide were classified by taking a landslide on the southern slope of Washan stope as an example. The deformation displacement and speed of this slope as well as the duration subjected to heavy rainfall were generalized. Then, the instability model and warning threshold were established. The results show that the slope deformation is positively correlated with rainfall in accordance with the power function. The slope deformation velocity is in good agreement with the rainfall intensity. Furthermore, the landslide generally occurs after maximum rainfall intensity. The landslide stages were classified into three, namely, initial deformation, stable deformation, and accelerated deformation. The warning threshold of displacement was 20 mm within 6 h and 30 mm within 12 h. The speed threshold was 1.5 mm·h^-1 within 6 h and 2.5 mm·h^-1 within 12 h. The landslide curve on the stope was highly similar to geotechnical non-steady creep curve. "Sharp convex"and"step jump"phenomena occurred on the curve, which could cause slope slide particularly at the inflection point of the slope deformation displacement curve and convex point of the corresponding velocity curve. The research results can provide a scientific basis and reference for slope stability monitoring and failure mechanism of similar mines.