The invention discloses a drainage system with a one-in-four-out type distributing well and a drainage control method. The drainage system with the one-in-four-out type distributing well comprises a regulation and storage instrument, an online processing instrument and an integrated processing instrument, wherein the integrated processing instrument can replace the role of sewage treatment plant to process domestic sewage and initial rainwater stored in the regulation and storage instrument; the online processing instrument can process intermediate late rainwater. During application, the drainage system with the one-in-four-out type distributing well can meet the sewage discharge standards of turning input dirty water into output clean water; a provided control system can save manual operation during application, a control unit can automatically adjust a water conservancy switch, and the control system can reasonably control the opening degree of the water conservancy switch and related modules to achieve reasonable water discharge, so that flood carrying safety can be ensured, and meanwhile, dirty water or initial rainwater can be closed to a closure pipe and the regulation and storage instrument to the maximum degree.