The northeast Tibetan Plateau, functioning as an alpine pasture, has been influenced by prehistoric settlements for millennia. However, the extent to which climate and anthropogenic activities have shaped this rangeland remains contentious. Here, we present sedimentary ancient DNA evidence from Lake Donggi Cona sediment core, focusing on the trnL p6-loop region of vascular plants and the internal transcribed spacer (ITS1) region of nuclear ribosomal DNA for Poaceae and Cyperaceae. Our findings indicate that before 7.4 cal ka BP, the rangeland was characterized by alpine steppe with low richness, influenced by dry environmental conditions. By 7.4 cal ka BP, more taxa migrated to the study region, with a relatively high richness supported by a humid environment. The climate conditions, coupled with low grazing pressure, sustained a relatively high pastoral quality. Intensified nomadic activities after 4 cal ka BP contributed to a severe decline in pasture quality, characterized by a high abundance of poisonous taxa. This study highlights that both human activity and moisture availability contribute to the rangeland characteristic, with human activity as the predominant factor since 4 cal ka BP.