The invention discloses a feeding device of a circulating fluidized bed boiler. The feeding device comprises a concrete drainage pipe with an include angle with the horizontal plane, multiple columnsof steel plate assemblies used for guiding materials are arranged in the concrete drainage pipe, a gap is reserved between the adjacent steel plate assemblies, each steel plate assembly comprises multiple middle fixed steel plates, each middle fixed steel plate comprises a main plate with the lower side face attached to the inner wall of the concrete drainage pipe, the front ends of the main plates are provided with mounting plates thinner than the main plates, the mounting plates are provided with fastening bolts penetrating the mounting plates to be fixedly connected with the concrete drainage pipe, the rear ends of the main plates are provided with covering plates with the lower side faces flush with the upper side faces of the main plates, the length of the covering plates is larger than the length of the mounting plates, the middle fixed steel plates in the steel plate assemblies are mounted in the concrete drainage pipe, the covering plates of the adjacent middle fixed steel plates are attached to the upper side faces of the other main plates, and gaps are reserved between the mounting plates and the other main plates.