【Objective】The increase in global CO2 concentration and climate warming has accelerated changes in the global water cycle and led to changes in global precipitation patterns. The Qinghai-Tibetan Plateau (QTP) is highly sensitive to global climate change, and its precipitation patterns have also shifted in response to the global precipitation pattern. Soil microorganisms constitute an important part of the underground ecosystem and play key roles in the soil carbon and nutrient cycle. An in-depth understanding of the response of soil microorganisms to precipitation changes is vital for analyzing the internal mechanism of the impact of global climate change on ecosystem carbon and nutrient cycles. However, it is still unclear how precipitation changes affect soil microbial biomass carbon (MBC), nitrogen (MBN), phosphorus (MBP), and their stoichiometric ratios in the alpine grassland ecosystem of the QTP. Therefore, the current study aims to investigate the response mechanisms of soil microbial biomass and their stoichiometric ratios to precipitation changes in an alpine meadow of the QTP. 【Method】A field manipulation experiment simulating precipitation variations was conducted in an alpine meadow of Hongyuan County, Sichuan Province. Five precipitation gradient treatments were established: a 90% decrease in precipitation (0.1P), a 50% decrease in precipitation (0.5P), a 30% decrease in precipitation (0.7P), a control (1P), and a 50% increase in precipitation (1.5P). Rhizosphere soil was collected in each precipitation gradient treatment. Soil MBC, MBN, and MBP content were determined by the chloroform fumigation method. Soil microbial biomass stoichiometric ratios were calculated by the soil MBC, MBN, and MBP content. At the same time, soil physicochemical properties, including soil water content (SWC), soil pH, soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), dissolved organic carbon (DOC), ammonium nitrogen (NH4+-N), nitrate nitrogen (NO3−-N), and available phosphorus (AP) were also determined. 【Result】The results showed that: (1) Soil MBC and MBN contents were increased with the increase of precipitation; however, MBP was not changed along the precipitation gradient. Compared with the control (1P), soil MBC and MBN content were significantly reduced in the 0.1P treatment; (2) Soil MBC∶MBN and MBC∶MBP showed an increasing trend with the increase of precipitation. The 0.1P treatment significantly reduced the MBC∶MBP ratio when compared with control; (3) Pearson correlation analysis showed that soil MBC, MBN, and MBP content were significantly positively correlated with SWC, and the MBC and MBN content were also significantly positively correlated with NO3−-N and negatively correlated with DOC. The MBC∶MBP and MBN∶MBP were significantly positively correlated with soil C∶N; (4) Multiple linear regression analysis showed that DOC had a significant negative effect on MBC and MBN, while TP and soil N∶P had significant positive effects on MBC and MBN. SWC showed a significant positive effect on MBN and MBP, while the soil C∶N showed a significant negative effect on MBP. Soil DOC and SWC had significant negative effects on MBC∶MBN, and soil C∶N had significant positive effects on MBC∶MBP and MBN∶MBP. 【Conclusion】Our study demonstrates that soil moisture and soil nutrients drive the dynamic response of soil microbial biomass to precipitation changes in the alpine grassland ecosystem of the Qinghai-Tibetan Plateau. By understanding the response mechanism of soil microbial biomass to precipitation changes, we can better predict and respond to the potential impacts of climate change on alpine ecosystems, and develop more effective ecological protection and management strategies to maintain the balance and sustainable development of alpine ecosystems. Therefore, this study provides a microbiological theoretical basis for the management of alpine ecosystems in the context of climate change.