The invention relates to a mounting method of a prefabricated capping beam sleeve and a bottom plate. The method comprises the following steps: manufacturing the bottom plate and the sleeve in a combining manner; integrally binding a reinforced cage and the bottom plate; integrally assembling the combined reinforced cage and the bottom plate into a die; positioning a concrete cushion block on a contact surface of a bottom die; and controlling the fitting degree of the bottom plate and the bottom die while the bottom plate is assembled into the die. With the adoption of the mounting method of the prefabricated capping beam sleeve and bottom plate, the accuracy of the reinforced cage assembled into the die can be ensured to the maximum on the premise that the construction requirements are met, and the time of assembling the reinforced concrete into the die is reduced.