Abstract: County-level urban-rural integrated development is a crucial approach for breaking the dual urban-rural structure, revitalizing rural economy, promoting the two-way flow of factors between urban and rural areas, and achieving equal access to public services. It holds significant strategic importance for fostering regional coordinated development and common prosperity. This study examines 431 county-level cities in the Yellow River Basin, utilizing a panel data from 2012 to 2023 and applies the entropy method, Dagum Gini coefficient, Moran’s I, and geographical detector to comprehensively analyze the spatiotemporal evolution and driving factors of urban-rural integrated development at the county level in the region. Results show that: 1) The overall level of urban-rural integrated development in the Yellow River Basin shows an upward trend, yet significant heterogeneity exists, with a spatial distribution characterized by a “lower reach > middle reach > upper reach” gradient; 2) The overall regional disparity exhibited a converging trend from 2012 to 2020, but widened sharply from 2020 to 2023 due to diverging internal development dynamics. The dominant role of “between-group differences” gradually weakened, while the contribution of “within-group differences” increased annually. Additionally, the spatial agglomeration effect of urban-rural integration significantly declined; and 3) Geographical detector results indicate that population size and government support are the core driving factors of county-level urban-rural integrated development. The interactions between these factors exhibit a two-factor enhancement effect, with population size, in particular, serving as a key factor that significantly amplifies the effects of other factors. Therefore, to holistically advance urban-rural integration in the Yellow River Basin, this paper suggests implementing targeted and categorized measures based on the coordinated development of “people-land-industry” at the county level as the key focal point.