With the implementation of landslide monitoring and early warning project, effective identification and utilization of monitoring information is becoming a key research issue in landslide predictions. It’s found that cumulative displacement-time curve of partial landslide fluctuates strongly under the action of reservoir water, and great differences exist between plane motion trajectory and main sliding direction. As a result, errors would occur in the results of landslide stability and prediction by analyzing cumulative displacement or projecting displacement vector onto the main sliding direction. The variation features of displacement vector of Jiaojiawan landslide in Three Gorges Reservoir area is simulated by FLAC3D. The results show that the real motion trajectory of landslide monitoring points can be reflected by analyzing the variation features of displacement vector. This research would be referential for the analysis of landslide monitoring data.