Abstract: In order to reveal the deformation evolution trend and reactivation mechanism of the reservoir bank landslide during the impoundment period, two-dimensional deformation was extracted based on SBAS-InSAR technology and 73 scenes of Sentinel-1 images from January 2021 to August 2022 during the impoundment period in Wulipo landslide area of the Baihetan reservoir. And an unmanned aerial vehicle (UAV) surveying technology was used to investigate the landslide and secondary hazards traces. Then, the GNSS displacement measurement data were utilized to compare and complement the InSAR displacement results. Finally, integrating the three technique results with the measured reservoir water level data and geological information, the state of Wulipo landslide was analyzed comprehensively. The results show that (1) The deformation of the Wulipo landslide is strongly correlated with the reservoir impoundment. There is no significant deformation occurrence before the impoundment, but visible deformation can be observed just one month after the impoundment. Increasing along with the water level, the maximum InSAR displacement rate in the slope direction can reach up to 153 mm/a and the maximum cumulative InSAR displacement can reach 121 mm in the radar line of sight direction, behaving a traction-type landslide character from lower deformation gradually to upper deformation. Analyzing by the integration of the measured water level data with GNSS displacement monitoring data, it is found obviously that there is a stronger correlation between the landslide deformation and the water level change during the impoundment period. (2) According to field geological investigation result, the Wulipo landslide is an inclined reverse rock mass slope with a hard upper section and a soft lower section, exhibiting an intense weathering on the rock of slope surface. A traction-type sliding can take place along the weathering layer due to the effect of the reservoir water on the lower rock mass, causing it soften and compression displacement. The research results can provide a scientific basis for the monitoring and prevention of reservoir bank landslides during the impoundment period.