The invention discloses an adjustable dual-blade floating boring tool for an ultralarge-aperture deep hole. The adjustable dual-blade floating boring tool comprises a fixed blade, a movable blade, tool teeth, fastening screws and a locating blade. The tool teeth of hard alloy materials are arranged at the upper end of the fixed blade and the upper end of the movable blade. A rectangular sliding groove is formed in the fixed blade, and fixed threaded holes are formed in the rectangular sliding groove. Kidney-shaped step holes are formed in the movable blade and are strip-shaped holes, and adjusting threaded holes are formed in the end face of the movable blade. The movable blade is mounted in the rectangular sliding groove. The fastening screws penetrate through the kidney-shaped step holesto be connected with the fixed threaded holes. The locating screw is mounted in the adjusting threaded holes, and the end of the locating screw abuts against the end face of the fixed blade. By meansof the adjustable dual-blade floating boring tool, the machining precision of the ultralarge hole can be greatly improved, and the problem that the machining precision is low in the prior art is solved.