Thourgh calculating the regional equilibrium line altitude, where long-term glacier mass gain equals mass loss，glacial damms may have played an important role in the stability of the plateau border and triggered outburst floods. There was ever a large ancestral ice-dammed lake at the entrance of Tsangpo gorge and many megafloods down Tasangpo gorge during the last glaciation. Those are important for understanding that hypothesis. But there is till lack of detail study for the age of dammed lake and the number of floods. Based on pramary work, the systematic OSL dating of lacustrine deposits will be made for its formation age and duration time. Three typical sections of lacustrine deposits were seclected for analizing sedimentary macrostructure in the field, microstructure under the microscope, and paleomagnetic secular variation. These are the evidence for many floods. This study provides time scale and direct evidence of multiple outburst flood for quantitative evaluation the glacial dam effects Tsangpo gorge surface processes.