The invention discloses a bridge deck drainage supporting facility. A drainage channel is formed in the outer side of a bridge deck pavement edge curb and provided with an open rectangular section, a footpath cover plate covers the upper portion of the drainage channel, the outside of the drainage channel is wrapped with a stainless steel plate, rainwater holes are formed in the curb, the drainage channel extends into linking roads at two ends of a bridge along the bridge, a spherical rubber expansion joint for water passage is formed in the position of the drainage channel passing an expansion seam, two ends of the rubber expansion joint are fastened on vertical seal head steel plates of the drainage channel through flange plates and bolts, openings are formed in the vertical seal head steel plates of the drainage channel and correspond to the expansion joint, the stainless steel plate externally wrapping the drainage channel is crimped at the openings of the seal head steel plates, the stainless steel plate, the rubber expansion joint and the flange plates are jointly anchored on a steel plate, a plurality of spheres are formed on the vertical surface of the rubber expansion joint, the displacement deformation requirement of beams on two sides of the expansion seam is met, and the cross section of the expansion joint is rectangular. The bridge deck drainage supporting facility can solve the problems that a drainage pipe of a traditional bridge deck drainage scheme is exposed, joints frequently leak and the like.