A thrust converting mechanism for a gauge-changing wheelset of a train, comprising: a mounting base, provided with a horizontal through hole along a horizontal direction; and a jacking shaft, movably disposed in the horizontal through hole in a penetrating manner, an open hole being provided in one of the jacking shaft and the mounting base at an engagement position between the jacking shaft and the mounting base, the open hole having an axis perpendicular to an axis of the horizontal through hole, a positioning piece being mounted in the open hole and connected with the open hole by an elastic preloaded piece; the other one of the jacking shaft and the mounting base being provided with a positioning recess matched with a positioning end of the positioning piece; wherein when the positioning end of the positioning piece is located in the positioning recess, the jacking shaft is in a locked state; when the jacking shaft is subjected to a thrust so that the positioning end of the positioning piece disengages from the positioning recess, the jacking shaft is in a movable state; characterised in that the mounting base comprises a base body and an extending base extending to a side along the base body, and the base body and the extending base are connected by a frustum-shaped transition connecting base having a large end connected with the base body and a small end connected with the extending base, and a periphery of the base body is provided with connecting holes allowing connecting pieces to pass through in order to mount the base body on the outer end of an axle-box body, and the horizontal through hole penetrates through the extending base, the transition connecting base and the base body. a mounting base, provided with a horizontal through hole along a horizontal direction; and a jacking shaft, movably disposed in the horizontal through hole in a penetrating manner, an open hole being provided in one of the jacking shaft and the mounting base at an engagement position between the jacking shaft and the mounting base, the open hole having an axis perpendicular to an axis of the horizontal through hole, a positioning piece being mounted in the open hole and connected with the open hole by an elastic preloaded piece; the other one of the jacking shaft and the mounting base being provided with a positioning recess matched with a positioning end of the positioning piece; wherein when the positioning end of the positioning piece is located in the positioning recess, the jacking shaft is in a locked state; when the jacking shaft is subjected to a thrust so that the positioning end of the positioning piece disengages from the positioning recess, the jacking shaft is in a movable state; characterised in that the mounting base comprises a base body and an extending base extending to a side along the base body, and the base body and the extending base are connected by a frustum-shaped transition connecting base having a large end connected with the base body and a small end connected with the extending base, and a periphery of the base body is provided with connecting holes allowing connecting pieces to pass through in order to mount the base body on the outer end of an axle-box body, and the horizontal through hole penetrates through the extending base, the transition connecting base and the base body.