On the basis of field investigation and former studies,the geological structures and seismicity in Xiaolangdi reservoir and its adjacent area are analysed.It is considered that the geotectonic background is complex and seismicity is relatively week in the area. By using probabilistic statistic method, logic information method and gray cluster method, possibility and magnitude of induced earthquake of the Xiaolangdi reservoir are forecasted.The result shows that there is the possibility of the induced events,especially in the middle segment of the reservoir and the maximum magnitude could be 5.0.