The invention relates to a viaduct drop-off deformation seam structure, which is arranged between a box type steel structure and a concrete structure, wherein one side of the concrete structure corresponding to the box type steel structure is fixedly provided with an embedded steel element, a steel support seat facing the inside of a deformation steam is correspondingly welded with the upper part of the embedded steel element and the upper part of the box type steel structure, waterproof coiled materials are paved on the steel support seat in the through length direction of the deformation seam, a steel press plate is placed on the waterproof coiled materials, and asphalt paste is respectively embedded in junction parts of the two sides of the steel press plate with the box type steel structure and the concrete structure. A groove-shaped layer board is arranged in the through length direction at the lower part of the deformation seam, one side of the groove-shaped layer board is connected with a lower wing edge of the box type steel structure, the other side of the groove-shaped layer board is fixedly connected with a hanging connecting element provided with a bent hook at the bottom end, and the upper end of the hanging connecting element is fixedly connected with the steel support seat arranged at one side of the concrete structure. The viaduct drop-off deformation seam structure solves the technical problems that the traditional pavement deformation seam structure cannot meet the requirement of various kinds of protection performance of the pavement deformation seam between a drop-off platform and a viaduct of a railway station building viaduct waiting hall under the deformation condition.