The invention provides a prestress assembled rail beam for stations and a construction method thereof. The prestress assembled rail beam comprises a rail beam main body; the rail beam main body comprises a flange, and two rib beams vertically connected to the flange; the two rib beams are oppositely arranged to form the rail beam main body with a double-T type cross section; and steel strands arearranged in the two longitudinal beams in a longitudinal penetrating mode. The prestress assembled rail beam is reasonable in structure and convenient to construct, and solves the defects in traditional bridge construction combination and bridge construction separation systems. Compared with a cast-in-place reinforced concrete structure, the structure height can be reduced, and the station hall floor escalator lifting height is reduced; and compared with a rail beam structure with bridge construction separation, a bracket can be not used, so that the maintenance and replacement difficulty of the bracket after operation of the stations is solved. The invention can be widely applied to rail beam structures of the stations.