Land use change has been demonstrated to be a key driver of soil acidification. However, there is a lack of systematic research on the interfering factors that continue to exacerbate soil acidification following land use change. Here, we compiled a soil pH dataset, including data from the Second National Soil Survey (1980s) and China Soil Series Survey (2010s), and employed a combined approach of machine learning and analysis of variance to elucidate the spatial variability of soil acidification and its influencing factors in subtropical China over the past 30 years under the context of land use change. The results indicated that over the three decades, both topsoil (0-20 cm) and subsoil (20-40 cm) have experienced severe acidification. Soil acidification following the conversion of agricultural land (paddy field and dryland) to woodland depends on the buffering capacity of the parent material. The interaction between land use change and nitrogen input (nitrogen deposition and nitrogen fertilizer application) significantly affected soil pH changes in the topsoil. Specifically, when the nitrogen input decreased by more than 50 kg N ha-1 year-1, soil pH of woodland converted to agricultural land increased, i.e., acidification was reversed. Our study results support the pursuit of a balance among agricultural land, tillage management, and climate change under the condition of stabilizing soil fertility, from which policymakers and farmers can benefit.