Landslide deposits have been observed to reactivate in association with water level fluctuations of reservoirs. The Shiliushubao landslide is an example of a mass movement where an accelerated deformation rate was triggered by the impoundment of a reservoir (the Three Gorges Reservoir in this case). This work investigated the relationship between the stability of this landslide and the variation in the reservoir water level. The stability of the landslide after reservoir impoundment was evaluated from February 2004 to December 2009 based on a sensitivity analysis of the hydraulic conductivity and the fluctuations in the level of the reservoir. The results suggest that the stability of the landslide is influenced by the rate of fluctuation in the level of the reservoir and the hydraulic conductivity. When the surface displacement monitoring data was integrated with the numerical modeling results, it became apparent that the stability of the Shiliushubao landslide increases as the reservoir water level is increased, whereas it decreases as the reservoir water level is lowered to avoid a dam breach during flood season.