The invention relates to a system for simulating the regional rainfall process, which comprises a hydro-meteorological database, a rainfall process generation subsystem, a rainfall process control subsystem and a rainfall simulation subsystem, and further comprises a regional climate model database, a station information database, a regional climate model, a station information interpolation device, a scale transformation device, a water spray control device, a water supplying device, a spray device, and a sensor mounted on a regional physical model, wherein spray units are arranged crosswise to form a spray unit array. Through the integration of the hydro-meteorological database, the rainfall process generation subsystem, the rainfall process control system and the rainfall simulation units, the generation and the simulation of the past, present and future rainfall processes in the designated area are achieved. The natural rainfall process can be better simulated, and the system has an important scientific research value in the fields of the watershed runoff generation and flow routing process, the research on hydrology and water resources in the lack-data watershed, the inspection and the optimization of the hydrographic station net arrangement, and the intelligence watershed research, and provides a scientific tool for simulation study and application of the regional hydrology.