In recent decades, the Qinghai-Tibetan Plateau (QTP) has been experiencing extensive and profound climate change, which would significantly affect phenology and distribution pattern of local species. Artemisia scoparia is a dominant species and key species affecting community stability in arid and semi-arid areas. The eastern edge of QTP is one of its important distribution areas. How the phenology of Artemisia scoparia responds to climate change is still an unsettled question. Therefore, the meteorological data and in-situ phenological observation experiments of 20 consecutive years on the eastern QTP were conducted to explore the dynamics of phenology of Artemisia selengensis and quantify the relative importance of different climatic factors. The results showed that: 1) In the past 20 years, the average annual temperature and average annual daily sunshine duration presented significantly upward and downward trends respectively, while annual precipitation and average annual daily maximum wind speed did not change significantly; 2) The intervals from greening-up to flowering and from flowering to fruiting of Artemisia selengensis did not show any significant trends in the past 20 years, while the interval from fruiting to withering was significantly shortened; 3) All climatic factors had significant effects on the intervals of different phenology of Artemisia selengensis, and the maximum wind speed was the most important climatic factor affecting the phenology of Artemisia selengensis. The study could provide a theoretical basis for the protection and utilization of alpine plants on the QTP under climate change.