The invention relates to the technical field of assembling tools, in particular to an assembling mechanism for hydraulic retarder blocking plates. The assembling mechanism for the hydraulic retarder blocking plates comprises a cylindrical aluminum rod, a rectangular aluminum plate, a plurality of short bolts, a long bolt, a nut and the like, wherein the cylindrical aluminum rod plays a main supporting role, the two ends of the cylindrical aluminum rod are provided with bosses, and the middle of the cylindrical aluminum rod is provided with a groove. The assembling mechanism is simple in structure, light, convenient to machine and use, high in reliability, and capable of achieving high-efficiency assembling of all the blocking plates and saving assembling time. The assembling mechanism can be used for rapidly installing no-load loss reduction blocking plate mechanisms of hydraulic retarder fixed wheels, meet the requirement for assembling of a hydraulic retarder system, achieve rapid installation, guarantee assembling quality, and lay a foundation for acceleration of development of hydraulic retarder products with low no-load losses.