The invention relates to a multistage baffled rainwater garden system used for processing initial rainwater and application of the multistage baffled rainwater garden system.The system comprises a filter area, multiple stages of baffled areas and an infiltration and reuse area which are sequentially connected in series.A non-overflow partition is arranged between the filter area and the first baffled area.The bottom of the filter area is communicated with the bottom of the first-stage baffled area.Overflow partitions are arranged between the odd-number baffled areas and the even-number baffled areas which are adjacent to the rear ends of the odd-number baffled areas.Non-overflow partitions are arranged between the even-number baffled areas and the odd-number baffled areas adjacent to the rear ends of the even-number baffled areas.The bottoms of the even-number baffled areas are communicated with the bottoms of the even-number baffled areas adjacent to the rear ends of the even-number baffled areas.An overflow partition is arranged between the last stage of baffled area and the infiltration and reuse area.The system can be suitable for gardens, communities, schools, urban green lands and the like, and pollutant in initial rainwater can be effectively processed; meanwhile, processed clean rainwater can infiltrate underground or be collected to be reused, and therefore the runoff volume and the runoff peak value are decreased, and the aims of environment protection and landscape improvements are achieved.