Abstract: At present, the impacts of high-speed railways (HSRs) on cities along rail lines remain unclear. Previous analyses of these impacts based on remote sensing data focused primarily on qualitative assessment. Given this, this study investigated the Hebei section of the Beijing-Guangzhou HSR and introduced a remote sensing monitoring-based method that integrated qualitative and quantitative analyses for assessing the impacts of HSR on urban development. First, this study established a parameter index system used to characterize urban development changes. Then, multi-source and multi-scale remote sensing data were employed to monitor the spatiotemporal variations in these indices before and after the operation of the Beijing-Guangzhou HSR within this study area. Finally, four cities that were adjacent to the study area but lacked available HSRs were selected as a control group. Using the difference-in-differences (DID) model, this study quantified the impacts of HSRs on four cities along the Hebei section. The results indicate that the four cities along the Hebei section of the Beijing-Guangzhou HSR saw a rapid expansion in the construction land between 2005 and 2020, with an average annual expansion rate of 2.00%. The HSR construction exerted a significant impact on the direction of urban expansion, with the impact related to the spatial relationship between both. Compared to the four cities in the control group, the operation of the Beijing-Guangzhou HSR has slowed down the expansion rates of urban areas in the four cities along the line.