Abstract: Using the geologic record of the ancient dammed lake sediments for regional climate and environment characteristic is a kind of new way.It is different from through deep ocean,polar ice core,loess,lakes,stalagmites,coral etc sediments geological record study of global climate change.Many substitution indexes reflect the environmental information of sediments.Sediment granularity is one of these indexes.It can reflect the pale-environment and pale-climate characteristics in the sedimentary process.In the eastern edge of Qinghai-Tibet Plateau 20, 000 years,the climate-environment evolution and the geological environment evolution are established.The precise granularity analysis and systematic granularity analysis were used to extract the granularity information in the ancient dammed lake sediments,and glacial lake sediments with the existing research results were compared.Through the study,the following conclusions: Diexi ancient dammed lake sediments are semi-diagenetic(unconsolidated soil)materials,mostly composed of silt and clay grain sizes.Sedimentary bedding showed dark color and light colored alternating sedimentation features with rhythm-layer thickness between 2~5cm.Diexi ancient dammed lake sediments have different characteristics from loess and glacial lake sediments.Based on bed sizes and color,combined with organic tests,we found out that dark-colored coarse particles in the ancient dammed lake sediments were accumulated in an environment that has abundant rainfall and lush vegetation; while light-colored fine particles were accumulated in arid climate with relatively sparse vegetations.Systematic study of granularity on sediment profile showed that there were 7 cyclical changes in granularity,revealing 7 climate and environment changes the region experienced during the entire deposition process.