The invention relates to an intra-mold labeling system. A label bin upward climbing mechanism for a lateral feeding type intra-mold labeling system comprises an upward climbing base and an upward climbing mechanism, wherein the upward climbing base comprises a rear fixing board, a front fixing board, a cylinder, parallel slide guide rods, supporting bars and a rack; the supporting bars are inclined; the rack and the slide guide rods are parallel; the cylinder is used for driving the rack to horizontally move in a reciprocating mode; the upward climbing mechanism comprises a push board and a slide block which are located above the supporting bars; the slide block is provided with a gear engaged with the rack and provided with at least one pair of clamping blocks clamped on the slide guide rods; and the gear is connected with the slide block through a drive one-way bearing. The label bin upward climbing mechanism for the lateral feeding type intra-mold labeling system and a label feedingmethod thereof aim to solve the problem that when an existing lower discharging label bin is used for large-area labels, poor labels are easily caused.