A door grating extension/contraction structure includes a frame and an extension/contraction mechanism. The frame is comprised of a plurality of bars. The extension/contraction mechanism is mounted to two parallel bars of the frame and is comprised of a telescopic tube set and a release assembly, wherein the telescopic tube set comprises a movable rod and the release assembly is coupled to the telescopic tube set and comprises a release button, a pawl member, and a transmission unit. The release button is coupled with the transmission unit and the transmission unit is coupled with the pawl member to form a resilient interconnection. The pawl member corresponds to and selectively forms an adjustable engagement with the movable rod of the telescopic tube set. The release button is operative to control engagement and disengagement between the pawl member and the movable rod, whereby the extension/contraction mechanism that is coupled to the frame can realize one-way or two-way extension/contraction to provide the door grating extension/contraction structure.