In sponge city construction in China, rainfall data is the basis for determining rainwater source control objectives. However, drastic change in rainfall caused by urbanization and climate change has dramatically reduced the rainfall data's representativeness. This study examines the impact of spatial-temporal rainfall changes over the past 50 years and evaluates the influence on the stability of rainwater source control effects in Beijing. The result shows that the rainfall variation trends differ in different regions in Beijing. In most areas, stable Volume Capture Ratio (VCR) cannot be achieved by a fixed size design rainfall depth, and highly urbanized areas are the most sensitive on source control effect. The design rainfall obtained from recent rainfall records may be on the low side, and the design rainfall should be increased to some extent to meet the 85% VCR goal in the future. Changping, Fangshan, Huairou, Mentougou, Yanqing have large spatial differences in design rainfall, and more attention should be paid to spatial differences in design rainfall.