Analyzing urban construction land expansion in China's urban agglomerations over the past 30 years is crucial for optimizing spatial patterns and promoting regional development. The study focused on 19 city clusters, using remote sensing data to extract urban areas and investigate expansion processes, development stages, expansion patterns, and center migration. Findings show that city clusters expanded slowly, rapidly, then stabilized, with eastern clusters expanding faster than western ones. By 2020, all clusters were in advanced development stages, with improved coordination between central and peripheral cities. Expansion patterns varied, with most clusters showing stable center positions and strong core city attraction. Monitoring urban development over time provides valuable insights for high-quality spatial planning and decision-making in city clusters.