The invention discloses an assembling deice of a water spraying propelling device and belongs to the technical field of ship power equipment. The assembling device comprises a tool rack, an inflow pipeline supporting tool, a bearing pedestal supporting tool, an inflow pipeline mounting and positioning tool, a main shaft auxiliary supporting tool, a main shaft mounting and positioning tool and an assembling platform. According to the assembling device disclosed by the invention, the tool rack is arranged to support an inflow pipeline and an impeller hood; the inflow pipeline supporting tool isarranged to support the inflow pipeline; the inflow pipeline mounting and positioning tool is arranged to position the inflow pipeline axially and radially so as to reduce the assembling error of theinflow pipeline; the bearing pedestal supporting tool is arranged to support the forecastle end of the main shaft; the main shaft auxiliary supporting tool is arranged to support the forecastle end ofthe main shaft; the main shaft mounting and positioning tool is arranged to position the main shaft radially to reduce deflection of the forecastle end of the main shaft, so that a guide vane nozzleand the forecastle end of the main shaft are mounted conveniently, and the assembling efficiency and the assembling precision of the water spraying propelling device are improved.