Taking an example of Yanziping Landslide in Jiudian Gorge reservoir in Gansu Province ,the paper applied a new kind of monitoring method (GPS) to analyze the law of influence of reservoir storage on landslide stability through the analysis of deformation monitoring. The results show that when the storage level is in the phase of 70 to 100 meters,the storage is unfavorable to the stability of reservoir landslide,but when the storage is in a certain height, the reservoir landslide will tend to stable;in low water level phase,the stability of landslide is less affected by reservoir storage; the main types of bank instability due to reservoir storage has three categories: resurrection sliding of preexisting landslide, new reservoir bank landslide and bank collapse.