The Dadu River Basin features a complex geological environment where landslide hazards are jointly controlled by multiple factors, including steep terrain, loose strata, active tectonics, and extreme rainfall, exhibiting significant regional differentiation. Based on SBAS-InSAR technology and multi-source data fusion analysis, it was found that 66.18% of the 2 377 identified landslides are small-scale, predominantly distributed in steep-slope areas such as Hanyuan and Danba. Seventeen active landslides were successfully identified and categorized into four types according to their deformation mechanisms: reservoir-aggravated accumulation landslides, reservoir-induced accumulation landslides, reservoir-induced bedding rock landslides, and reservoir-induced toppling deformation landslides. Case studies indicate that a rapid rise in reservoir water level can reactivate landslides through a triple mechanism of toe erosion, seepage field alteration, and rock mass softening. Time-series deformation analysis reveals a synergistic disaster-inducing mechanism between water-level fluctuations and rainfall. It is recommended to mitigate risks through the establishment of a dynamic monitoring system, optimization of reservoir water-level regulation, and implementation of integrated engineering-ecological control measures. The results provide theoretical support for landslide risk management in reservoir areas.