The invention discloses a producing method for a composite steel pipe and a water-carrying deburring machine applying the same. According to the technical scheme, the producing method is characterizedby sequentially comprising the following steps of steel coil processing, steel coil striping, welding pipe forming, fixed-length cutting, and cutting opening deburring. The water-carrying deburring machine comprises a storing seat, a polishing seat arranged at one end of the upper surface of the storing seat, a driving device rotatably arranged on a rotating body of the polishing seat and drivingthe rotating body to rotate, and an inner polishing block and an outer polishing block arranged at the polishing end of the rotating body, a spacing adjusting piece is arranged between the inner polishing block and the outer polishing block, the water-carrying deburring machine further comprises a water seeping assembly arranged between the rotating body, the inner polishing block and the outer polishing block, and the water-carrying deburring machine further comprises a clamping seat, a plurality of inner clamping plates and a plurality of outer clamping plates oppositely arranged on the clamping seat through a synchronous clamping assembly. According to the processing method and the water-carrying deburring machine, a steel plate is prefabricated, then the steel plate is processed intoa pipe, the quality of the steel pipe is controlled by controlling the quality of the steel plate, the operation is more convenient, the special water-carrying deburring machine is used for polishingthe steel pipe, and the quality pass rate of the steel pipe is high.