The invention discloses a river channel water body sewage disposal device. The technical problems that an automatic grillage machine is erected in a riverbed for being used in existing current marketcondition and application, functions of the automatic grillage machine are that large floating objects are removed, automatic slag salvaging and automatic transmission are achieved, river channel passing is affected, the project is huge, and flood cannot be eliminated are solved. According to the technical scheme, the river channel water body sewage disposal device comprises a movable type collection device fixed into the riverbed and used for cutting off the floating objects, a self-spraying cleaning device located in the collection device, a sewage storage groove located at one end of the collection device and a sewage lifting pump located in the sewage storage groove; the collection device comprises a sealed collecting groove enclosed by grids, a transmission chain arranged at the upperend of the collection groove and more than one power transmission device driving the transmission chain to transmit located in the collection device; and the collection groove moves with the transmission chain, and the depth of the collection groove is equal to the depth of the riverbed.