Structure and construction method of newly-added prefabricated guardrail of existing bridge

The invention discloses a structure and a construction method of a newly-added prefabricated guardrail of an existing bridge. The structure of the newly-added prefabricated guardrail of the existing bridge comprises a main beam, wherein a plurality of first reinforcing steel bars are arranged in the main beam; a base, wherein a first steel plate and a plurality of second reinforcements are arranged in the base, and the second reinforcements are connected with the first reinforcements and the first steel plate; a guardrail which is provided with a second steel plate and a plurality of third reinforcing steel bars, the third reinforcing steel bars are embedded into the guardrail, the second steel plate is connected with the third reinforcing steel bars, the second steel plate is connected with the first steel plate, a shear key and a shear groove are arranged between the guardrail and the base, and the shear key can be embedded into the shear groove. The structure has the beneficial effects that the second stee