An adjustable supporting rod for a building early-removing supporting system comprises an outer tube and an inner tube, wherein the lower end of the inner tube is plugged inside the upper end of the outer tube, a plurality of inner tube positioning holes are formed in the inner tube, a plurality of outer tube positioning long holes corresponding to the inner tube positioning holes are formed in the outer tube, a circular ring is sleeved on the outer tube, a circular hole is formed in the circular ring, a positioning pin sequentially penetrates the circular hole, the outer tube positioning long hole and the inner tube positioning hole, so that the outer tube is connected with the inner tube; the upper end of the outer tube is in threaded connection with an adjusting nut, and the circular ring pushes against the adjusting nut; and the bottom of the outer tube is fixedly provided with a fixed plate. The adjustable supporting rod is simple in structure, no horizontal connecting rod is needed between the supporting rods, so that the installation time is reduced, the installation difficulty is lowered, the height of the supporting rod is adjustable, and simpleness in operation is realized.