The soil inorganic carbon (SIC) pool in the Qinghai-Tibetan Plateau (QTP) grasslands is approximately twice as large as the soil organic carbon, playing a critical role in China's terrestrial carbon balance. Despite its importance, SIC remains poorly quantified under climate change and atmospheric acid deposition. Here, we incorporate a module for proton production into a process-based soil inorganic carbon turnover model to assess the long-term impacts of atmospheric acid deposition on SIC dynamics in the QTP down to 30 cm depth through 2015-2100. We found a decrease of 87.67-122.29 Tg (7.75-10.81%) in SIC stock in the topsoil (0-10 cm) and 76.50-85.47 Tg (2.12-2.37%) in the 0-30 cm soils. Compared to climate change alone, acid deposition amplifies SIC loss in the topsoil by 15.46-41.28 Tg (1.37-3.65%), with a smaller effect in the 0-30 cm profile (0.05-0.17 Tg), which means a part of surface SIC loss deposit below 10 cm. The greatest ecological impacts due to acid deposition occur in semi-arid regions and grassland ecosystems, where SIC losses increase by 9.64 Tg (2.69%) and 15.70 Tg (2.41%), respectively. Among acidifying components, sulfur (S) deposition contributes 1.3 times as much to SIC loss as nitrogen (N) deposition. These findings isolate the effects of acid deposition on SIC and provide a quantitative basis for assessing the respective roles of N and S deposition, offering critical insights into ecosystem carbon cycling and informing future strategies to mitigate acidifying air pollution.