Abstract: Understanding the factors that control typhoon rainfall distribution is critical for improving rainfall forecasting, especially for landfall typhoons. This study investigated the impact of typhoon size on rainfall characteristics at landfall in eastern coast of China. Typhoons Ampil (2018) and Rumbia (2018), which had similar intensities, were investigated to explore the connection between storm size and rainfall. The larger cyclonic wind field in Typhoon Rumbia led to greater vorticity and broader convergence compared to Typhoon Ampil, along with an ascending region outside the eyewall, which promoted more vigorous rainbands. Rumbia′s larger size exhibited greater outer-core radial vorticity advection relative to Ampil. This maintained its extensive outer-core wind field and intensified outer rainband development. Consequently, Rumbia generated more extensive and prolonged rainfall post-landfall compared to Ampil. A composite analysis of typhoons making landfall in eastern China (2001‒2021) further examines the statistical correlation between typhoon size and rainfall distribution. Results indicate that larger typhoons are more likely to generate heavier and more spatially extensive rainfall in regions beyond their eyewalls. These findings highlight that typhoon size significantly regulates rainfall evolution during landfall, underscoring the necessity of incorporating this parameter into operational rainfall forecasting models for landfalling typhoons.