The invention discloses a mounting construction method for a buried water drain pipe of an urban bridge and relates to the technical field of drainage systems of overpasses. A box girder, a galvanizedsteel pipe and a pier stud are included specifically. Bridge pads are arranged on two sides below the box girder, the pier stud is placed below the bridge pads, and the galvanized steel pipe penetrates from inner sides of two sides of the box girder and inner sides of two sides of the pier stud, separately. According to the mounting construction method for the buried water drain pipe of the urbanbridge, the integral appearance of the whole overpass is damaged by a conventional exposed pvc drainage pipe of the bridge. By adopting the buried water drain pipe, the pier stud and the box girder tend to be harmonious further, so that the aesthetic degree is improved greatly and the integral effect between the box girder and the pier stud is improved. As the buried water drain pipe is mounted while the stud pier and the box girder are constructed synchronously, the water drain pipe can be mounted and fixed greatly by using a pier stud bracket or an inner mold support of the box girder, andthe water drain pipe is quite convenient to mount and fix, so that the construction period is also shortened greatly.