Global climate change affects hydrological processes by altering precipitation characteristics. However, existing studies have predominantly focused on the impacts of changes in total precipitation on hydrological processes, while analyses concerning changes in precipitation intensity and their effects remain relatively limited. To address this gap, this study utilizes the CRU global precipitation amount and frequency datasets from 1901 to 2021, and employs the Mann-Kendall trend test and abrupt change detection method to comprehensively analyze the spatiotemporal variation characteristics of global annual mean daily precipitation intensity. Furthermore, a physically-based Budyko water balance framework is adopted to develop a quantitative method for assessing the impact of precipitation intensity changes on the runoff coefficient, with the Pearl River, Nenjiang River, and Manas River basins serving as typical case studies for validation. The results indicate that: global annual mean daily precipitation intensity exhibited a significant increasing trend during 1901–2021; pronounced regional differences were observed among the 26 IPCC climate reference regions, with 13 regions showing increasing trends and 13 showing decreasing trends; abrupt change years of global annual mean daily precipitation intensity were primarily concentrated around the early 20th century (circa 1912) and the early 21st century (2009–2015); case studies of three typical basins demonstrated that the contribution of mean daily precipitation intensity to variations in the runoff coefficient was substantial in both the humid region (Pearl River) and the arid region (Manas River), while in the semi-humid to semi-arid transition zone (Nenjiang River), its contribution was intermediate between those of the aridity index and underlying surface conditions. These case studies indicate that mean daily precipitation intensity is a critical factor influencing runoff variations, and its impact on hydrological processes should not be neglected.