Abstract: Against the backdrop of climate change, conditional changes of rainfall may lead to the change of runoff production and confluence process, which in turn may influence the runoff control efficiency of the rainwater harvesting greenbelt. This thesis aims to analyze the past and future rainfall trends in the Qian’an area through climate inclination rate analysis and MK test. Using the Binhu East Road area of Qian’an City as the research object, it employs MIKE URBAN software to simulate the overflow load of the regional drainage system over different periods of rainfall before and after the establishment of the exogenous rainwater harvesting greenbelt. The paper also calculates the level of rainfall in the future return period so as to probe into the runoff control efficiency of the exogenous rainwater harvesting greenbelt affected by climate change. Conclusions are as follows: 1) Rainfall in Qian’an area has been on a rise ever since 1989, and it shall continue according to the future scenario simulation. 2) The overflow load of the regional drainage system in 1a, 2a, 3a and 5a areas shall be effectively mitigated after the establishment of the rainwater harvesting greenbelt. 3) The control efficiency of the exogenous rainwater harvesting greenbelt in response to future rainfall will be weakened. Overall, this paper proposes that climate change conditions should be taken into account in the planning and construction of sponge city to note the climate adaptability of low impact development system.