Various embodiments relate to a resetting mechanism for resetting a screw spindle of a drug delivery device including a driving element including two opposite driving pillars, connected to a sidewall and disposed in a chamber, a limiting element, movably engaged with the driving element, and two opposite clamping elements, movably disposed on two sides of the screw spindle, each of the clamping elements including a sliding base wherein the sliding base has a guide rail and a recess and a clamping jaw, connected to the sliding base and disposed in the chamber, wherein the opposite driving pillars slide in the guide rails along with the movement of the driving element, when the driving element moves toward the limiting element, the driving pillars drive the two clamping elements to move toward the screw spindle to make the two clamping jaws clamp the screw spindle and when the driving element moves away from the limiting element, the driving pillars drive the two clamping elements to move away from the screw spindle to make the two clamping jaws release the screw spindle.
