Abstract: The slope of Tanjiahe Landslide located in the Three Gorges Reservoir area has a special structure with complex formation mechanism.Since the monitoring began in December 2006,it has been constantly displacing and deforming.On the basis of analyzing the characteristics of Tanjiahe Landslide deformation(2015～2020),the GPS manual and GPS automatic monitoring data were finely divided into several stages by a qualitative and quantitative combined method, and the reservoir water level and rainfall data were analyzed and processed.By combining the groundwater level monitoring data, the response mechanism of landslide deformation was summarized, and the induced factors and mechanism of landslide were revealed.The results showed that:(1) The cumulative displacement of the Tanjiahe Landslide presented a steady-step increasing trend.Under the action of dead weight, reservoir water fluctuation and atmospheric rainfall, the sliding peristaltic deformation occurred in a way of easily-sliding block pushing forward the holding back block.The rise and fall of reservoir water level was the direct factor for landslide deformation, and rainfall played a role in promoting landslide deformation.The monthly rainfall in a flood season reached more than 160 mm for two consecutive months, promoting landslide deformation greatly.(2) When the reservoir water level dropped from 175.00 m to 160.00 m at a low speed, due to the weight reduction and soaking softening effect of the reservoir water, the slope deformation kept growing at a low speed.When the reservoir water level dropped rapidly from 160.00 m to 145.00 m, the greater the water level's drop rate, the greater the dynamic water pressure toward the slope surface, resulting in more obvious deformation of the slope.(3) In the low water level operation stage, because of a certain lag effect with rapid decline of reservoirs on the landslide deformation, the slope deformed constantly during the two 145.00 m low water level operations, and the deformation during the first low water level operation was stronger than that in the second one.(4) When the reservoir water level had rapidly risen from 145.00 m to 175.00 m, the rise of the reservoir water level was conducive to the stability of the slope under the condition of weak rainfall intensity.However, when the reservoir area was subjected to continuous rainfall, the stability of the slope would be reduced.Because the reservoir water exerted a significant lift force on the holding back block of the landslide, the slope deformation was aggravated.The research results can provide a reference for the induction mechanism analysis, monitoring, early warning and forecasting, and emergency treatment of water-related landslides in the Three Gorges Reservoir area.