City rail U type roof beam winter construction steam maintenance canopy device, include to cover the rack that has thermal -insulation exterior wall a plurality of support ribs that the slant set up between rack crossbeam and both sides stand are arranged along rack longitudinal separation, support the steam conduit that is provided with and supplies on the rib vapour device to be linked together, the spaced apart steam outlet hole that is equipped with on the steam conduit, thermal -insulation exterior wall has seted up the door in the side. The utility model has the advantage of simple structure, convenient to use only needs the rack scope to construction region of hoisting, with steam insert in the canopy in the steam pipe can, the internal operation space that not only has enough spaciousnesses of canopy, it is effectual to keep warm moreover. Cover the steam maintenance with traditional tarpaulin and compare, use the utility model discloses, the input of manpower, the material resources of having significantly reduced has improved work efficiency, has ensured construction quality.