There happened a scale of 8 on the Richter calculations earthquake in Wenchuan County, Sichuan Province on May 12th of 2008. It caused a lot of landslides in Beichuan County and many landslide-dammed lakes had been formed, some of the lakes are at very urgent risk of dam breaking and would threaten downstream people.Results of an investigation on landslide-dammed lakes are analyzed after Wenchuan earthquake using various types of remote sensing data including aerial, visual, and SAR satellitedata. This paper discusses the general role of distribution and variation of land slidedammedlakes.The dynamics of the Tangjiashan landslide-dammed Lake, which is the large stone, is analyzed indetail. Area changes of theTangjiashan landslide-dammed lake in different periods, including the course length and the water surface area of inundated region are obtained from images between May14th and 26th. The course length and the water surface area were about 7.39km and 1.14 km 2 on 14th May, respectively. By 26th May, the course length and the water surface area reached 17.6km and 4.09 km2 , respectively. The results provided basic information for disaster reduction of the landslide-dammed lakes in this region.