A sliding track assembly for a casing for installing an embedding object so that the embedding object can be pulled out or pushed thereto comprises a retaining unit having a front end and a rear end; each of the front end and the rear end having a plurality of through holes for locking the retaining unit to a casing; a base having a wall with a plurality of through holes; a sliding sleeve engaged to and slideable to the base; the sliding sleeve having a long hole; a supporting frame installed at an inner side of the sliding sleeve and having an ear; the ear having a plurality of retaining holes and a sliding groove corresponding to the long hole of the sliding sleeve; and a clamping unit installed at an outer side of the sliding sleeve.