The invention discloses a variable
diameter chamfering-based top plate high-
directional drilling gas extraction device, which comprises a
drill rod, an extraction drum, a
drill bit component, a variable
diameter chamfering component and a supporting component, wherein a center hole in one end, away from a
drill hole, of the drill rod is connected with a
water supply pipeline by a rotating joint; the
water supply pipeline can supply flushing fluid to the center hole of the drill rod; the extraction drum is arranged on the outer circumference of the drill rod in the
drill hole in a sleeving manner; during drilling and variable
diameter chamfering, gas in the
drill hole can enter the extraction drum, and is collected into an
external storage tank through a gas collection
pipe, thus realizingpreliminary extraction and preventing gas leakage; the drill rod is hermetically and rotatably arranged in the extraction drum; furthermore, one end, away from the
drill hole, of the drill rod is driven by an underground drill rig, and the other end of the drill rod is provided with the variable diameter chamfering component and the
drill bit component in sequence; meanwhile, during drilling and variable diameter chamfering, the drill rod extends into the drill hole, and then is supported by the supporting component into the inner wall of the drill hole.