The invention discloses a hydraulic control combined system channel sewage interception method which comprises the following steps: S1, building a pollutant intercepting dam in a combined system drainage channel for intercepting dry flow sewage and initial rainwater in the channel; S2, tapping on a side wall of the channel, and collecting the dry flow sewage and initial rainwater to a sewage interception main pipe by using a sewage interception pipe; S3, arranging a rectangular lightweight spring door at the sewage interception pipe orifice in the side wall of the combined system drainage channel. The pollutant intercepting dam is a mortared block stone dam or a concrete dam, and the height of the pollutant intercepting dam is 200-300mm larger than the diameter of the sewage interception pipe. Invert elevation of the sewage interception pipe is 150-200mm higher than invert elevation of the channel, and the hydraulic slope of the sewage interception pipe is 0.29-0.31%. The whole sewage interception method is simple in process, convenient in construction, economic and reasonable, automatically realizes control of the sewage interception amount by utilizing the hydraulic action, has the advantages of being reliable, durable in use, energy-saving, environmentally friendly, convenient in maintenance and the like, and is very suitable to be applied to combined system drainage channel renovation projects.