The invention discloses an urban small watershed classification and grading intelligent scheduling method. According to the invention, the method comprises the steps: taking rainfall forecast as a judgment condition; starting different scheduling modes according to the rainfall prediction situation, namely, rain-free starting ecological water supplementing scheduling, light rain starting water environment scheduling, medium rain starting water environment-flood prevention and drainage combined scheduling and heavy rain-rainstorm starting flood prevention and drainage scheduling; automaticallyswitching the scheduling modes along with the change of the rainfall situation, and dynamically adjusting the scheduling scheme. The complex comprehensive scheduling problem of the urban small watershed is decomposed through classified scheduling, so the processing scheduling target is clear, the scheduling model is simple, the calculation efficiency is higher, and the operability is higher; meanwhile, a simulation and optimization combined method is adopted, and a scheduling process is decomposed through a 'plan scheduling-optimal scheduling' two-stage scheduling mode, so the repeated trial process of an optimal scheduling scheme can be skipped, the time is saved, the efficiency is improved, and meanwhile, the method is more practical and more applicable to basic-level scheduling personnel.