The RK24 landslide is a typical case of transformed secondary landslide of shallow landslide transforming into a deep one, which is a secondary slide based on the existing engineering structure. Based on the detailed investigation of RK24 landslide, we analyzed its deformation characteristics, instability cause and control measures. The research results show that the limited monitoring data can accurately reflect the internal deformation of the sliding body with reasonable division of transverse and longitudinal of the sliding body, there are slide surfaces in the inflection points of deformation difference value, and there are cracks in the local abnormal points in the stable region. Abundant loose material source and dominant joint structure provide fundamental conditions. Rainfall or earthquake can trigger the transformed secondary landslide, and the shaking and disturbance in the process of construction and transportation force the transformation from shallow to deep. Control measures should consider comprehensively, including the depth of secondary slip surface, the reason of instability and the failure of existing engineering and so on. The measures of instability triggered by heavy rainfall should be enhanced drainage, and the measures of instability caused by shaking should be supported and reinforced further.