The invention relates to an in-mold labeling system and particularly relates to a climbing label bin of a side-in in-mold labeling system. The climbing label bin comprises a label bin frame, a climbing base and a climbing mechanism, wherein the climbing base comprises a rear fixed plate, a front fixed plate connected with the label bin frame, a cylinder, a sliding guide rod, support bars and a rack, wherein the sliding guide rod, the support bars and the rack are parallel to each other; the support bars are tilted; the rack is parallel to the sliding guide rod; the cylinder is used for drivingthe rack to do reciprocating horizontal motion; the climbing mechanism comprises a pushing plate located above the support bars and a sliding block; a gear meshed with the rack is arranged on the sliding block; at least one pair of clamping blocks clamped on the sliding guide rod are arranged on the sliding block; the gear is connected with the sliding block through a driving one-way bearing. Inorder to solve the problem that the defects of the labels are easily caused when the existing bottom discharge label bin is applied to large-area labels, the invention provides the climbing label binwhich is low in possibility of deformation and damage of the labels and is applied to the side-in in-mold labeling system and the label conveying method thereof.