Abstract: A secondary disaster early warning method based on ground-based SAR monitoring of deformation data includes (1) real-time monitoring of a secondary disaster unstable area through ground-based SAR to obtain deformation monitoring data; (2) constructing a displacement-time curve generated by the secondary disaster unstable area over time; setting a monitoring period, and based on the displacement-time curve, constructing a displacement change triangular area model; (3) based on the displacement change triangular area model, constructing an area-time curve, and obtaining the area-time curve change trend and the displacement triangular area in the displacement-time curve according to the monitoring period; (4) dividing the secondary disaster development process into an initial deformation stage, a constant velocity deformation stage, and an accelerated deformation stage; (5) setting early warning levels corresponding to each stage for phased secondary disaster early warning; and (6) quickly and comprehensively id