The invention provides a variable-height conveying line which comprises a support, a high-end conveying line, an inclined conveying line, a bottom-end conveying line and a lifting mechanism, wherein a first sliding track in the height direction of the support and a second sliding track perpendicular to the height direction of the support are arranged on the support; the high-end conveying line is slidingly connected with the first sliding track; one end of the inclined conveying line is arranged at the lower end of the high-end conveying line and slidingly connected with the first sliding track correspondingly; the other end of the inclined conveying line is arranged at the upper end of the bottom-end conveying line and slidingly connected with the second sliding track correspondingly; and at least a part of the inclined conveying line and at least a part of the bottom-end conveying line are overlapped. The problems that in the prior art, the height of a conveying line is not convenient to adjust, and device fixing and butt-joint of the device and other devices are not facilitated are solved; and the height drop of the variable-height conveying line can be changed continuously, and relative displacement cannot occur at two ends of the conveying line, so that device fixing and butt joint of the device and other devices as well as operation are facilitated.