This article uses a dataset covering the period from 220 B.C. to 1839 A.D. to investigate how natural environment influences political regimes through the channels of building Great Wall (national defense) and taming the Yellow River. The results obtained show that the presence of the autocratic monarch (or the weak prime minister) was caused by changes in weather patterns starting from the Song dynasty when the Chinese weather began to enter the Little Ice Age. The colder and extreme weather conditions worsened the living environment of northern nomadic people as well as increased the sediment concentration of the Yellow River. The former would, in turn, cause frequent Sino-nomadic conflicts, while the latter would increase the risk of the bank-breaching of the Yellow River. To address these two challenges, the Chinese political regime had to evolve toward a more autocratic and centralized state so as to ensure that limited resources were efficiently directed to prevent the nomadic invasions and the flood of the Yellow River. This kind of change in political regime in response to weather conditions is fully compatible with the law of evolution proposed by the neo-institutional school.