A inner sliding rail mounting structure is disclosed to include a control plate pivoted with a front side thereof to an inner sliding rail of a sliding track assembly for engagement with a stop block of an intermediate sliding rail of the sliding track assembly to secure the inner sliding rail to the intermediate sliding rail, a slide pivoted to the rear side of the control plate and coupled to the inner sliding rail by a slip joint for biasing the control plate to disengage the control plate from the stop block of the intermediate sliding rail for allowing removal of the inner sliding rail from the intermediately sliding rail, and a carriage affixed to the rear side of the slide and holding a spring member against a locating block at the inner sliding rail for pulling by the user to force the slide to bias the control plate.