The utility model discloses a clearance elimination device for double rack-and-pinion transmission of a numerically-controlled machine tool. The device comprises a first gear shaft with a first gear sleeve and a first expansion sleeve, a second gear shaft with a second gear sleeve and a second expansion sleeve, a third gear shaft, a forth gear shaft, a first gear and a second gear which are meshed with each other, wherein, the first gear is mounted on the second gear shaft, and the second gear is mounted on the forth gear shaft; the first gear sleeve and the first gear shaft are meshed with the outer side of the first gear; the second gear sleeve and the second gear shaft are meshed with the outer side of the second gear; and pin holes are formed on both the first gear sleeve and the second gear sleeve. The utility model can eliminate opposite clearance during the reciprocating linear movement of the machine tool, thereby ensuring operating precision of the linear movement of the machine tool. Moreover, the utility model has the advantages of simple and compact structure, reasonable use of space, stable operation and less transmission noise, and can be widely applied to various numerically-controlled machine tools adopting the method of gear-and-rack-rod transmission.