<p>In recent years, many studies have focused on the effects of global climate warming and increased nitrogen deposition on the structure and function of grassland ecosystem. However, there are still significant uncertainties in the response mechanism of stability of plant community biomass in alpine meadows of the Qinghai-Xizang Plateau, China to these two major climate factors. Given this, based on field control experiments, this study systematically evaluated the effects of different levels of climate warming (W0 (no warming), W1 (air temperature increased by 0.47°C or soil temperature increased by 0.61°C), W2 (air temperature increased by 0.92°C or soil temperature increased by 1.09°C), W3 (air temperature increased by 1.44°C or soil temperature increased by 1.95°C)), nitrogen deposition ((N0 (0 kg N/(hm²·a), N16 (16 kg N/(hm²·a), and N32 (32 kg N/(hm²·a)), and their interactions on plant community biomass and its temporal stability, and explored its potential regulatory mechanisms. The results showed that the biomass of total community, Gramineae, and dominant species increased significantly with increasing temperature, but the biomass of common and rare species decreased significantly. Nitrogen deposition also significantly promoted the biomass accumulation of community and gramineous plants. Under the treatment of W3N32, the biomass of plant community, Gramineae, and dominant species reached the highest values, indicating that there was a synergistic effect under this treatment. Structural equation model showed that increasing temperature significantly decreased the stability of plant community biomass by reducing the stability of grass and dominant species biomass and weakening species asynchronism. Interaction of increased nitrogen deposition and temperature increased the biomass fluctuation of grass functional group, thus amplifying its negative influence on community stability. More attention should be paid to the response and regulatory mechanisms of dominant species and functional groups under global climate change. This study provides a theoretical basis for revealing the stability maintenance mechanism of alpine grassland and also provides scientific support for the development of future grassland ecosystem management and assessment.</p>