The utility model provides a supporting construction that is used for tunnel to advance to be wide open and dig, cover including being located the tunnel portal top encircles, is located the tunnel portal both sides for support the expansion basis that the cover encircles, the cover encircles the pipe canopy that sets up a plurality of steel pipes constitutions on the steel bow member including the steel bow member and along the vault hoop, the both ends of steel bow member respectively with enlarge preformed reinforcement bar in the basis with welded mode fixed connection, the leading ductule of a plurality of roots has been inserted to the pipe canopy. The utility model discloses a supporting construction overall stability is strong, it can dynamic height, the wide model of application scope to strut, construction steps is simple, the efficiency of construction is high, construction cost low and factor of safety is high, can prevent effectively that tunnel portal from caving in and bian yangpo slides.