A municipal rainwater processing system comprises a water collection pipe, a rainwater well, a river water backflow retardation weir, a deposition pool and a pump station. The water collection pipe is used for collecting rainwater. The rainwater well is communicated with the water collection pipe, has the specific volume and can store the specific amount of rainwater collected by the water collection pipe. The rainwater well is communicated with a river way through a rainwater dredging pipe. The river water backflow retardation weir is arranged in the rainwater well. The deposition pool is used for depositing rainwater entering the deposition pool. The deposited rainwater can be discharged into the river way or a municipal sewage pipe network. The pump station is used for pumping rainwater to the deposition pool from the rainwater well. The rainwater well is communicated with the pump station through two outlets. The first outlet is formed in the bottom of the rainwater well. The second outlet is formed in the position of the half capacity water level of the rainwater well. The first outlet and the second outlet can be controlled to be opened and closed through a control device.