A packing machine core, comprising: a control mechanism, a packing strap ironing adhering and strap cutting mechanism, an ironing adhering sliding plate mechanism, and a machine core bracket, wherein the control mechanism comprises a machine core mainshaft and a mainshaft motor, multiple control cams (101, 102, 103, 104, 105) are mounted on the machine core mainshaft and have multiple cams for controlling the ironing adhering and strap cutting mechanism and a first cam for controlling a swinging arm of the ironing adhering sliding plate mechanism, the mainshaft motor drives, by means of a speed reducing mechanism, the machine core mainshaft to rotate, and the multiple cams for controlling the ironing adhering and strap cutting mechanism comprise a left cutter cam, a middle cutter cam, a right cutter cam, and a second cam for controlling a swinging arm of an ironing head to work; the packing strap ironing adhering and strap cutting mechanism is provided with a left cutter, a middle cutter and a right cutter which may move upward or downward, and the machine core bracket is provided with a guide structure for guiding the left cutter, the middle cutter and the right cutter to move upward or downward; characterized in that: the right cutter has a support head for supporting the packing strap and a hole, positioned underneath the support head of the right cutter, through which the packing strap passes, wherein a height of the hole is high enough to ensure that when a lower sliding plate is positioned above the middle cutter, the hole can be plugged by a limit slot in the lower sliding plate; the middle cutter has a support head thereof for supporting the packing strap, and a strap cutting fit is formed between an upper margin at a right side of the middle cutter and an upper margin at a left side of the hole mouth; and the left cutter has a support head thereof for supporting the packing strap; the swinging arm of the ironing adhering sliding plate mechanism and the swinging arm of the ironing head each is respectively positioned at a first side and a second side of the machine core, the left cutter, the middle cutter and the right cutter are positioned between the swinging arm of the ironing adhering sliding plate mechanism and the swinging arm of the ironing head, the first side is either of a front side and a rear side of the machine core, and the second side is either of the front side and the rear side of the machine core; the ironing adhering sliding plate mechanism comprises an upper sliding plate, a lower sliding plate and a sliding guide structure, wherein a front part of the lower sliding plate is corresponding to the middle cutter, a front part of the upper sliding plate is corresponding to the left cutter, the middle cutter and the right cutter, and the lower sliding plate is connected to a head limit part of a packing strip and a corresponding sensing element; the sliding guide structure comprises an upper guide structure for guiding the upper sliding plate to slide and a lower guide structure for guiding the lower sliding plate to slide; the sliding plate mechanism is further provided with a lower sliding plate seat on which the lower sliding plate is mounted, the swinging arm of the ironing adhering sliding plate mechanism is connected to the lower sliding plate seat, the lower sliding plate may slide relatively to the upper sliding plate, and the ironing adhering sliding plate mechanism is provided with a limit structure between the upper sliding plate and the lower sliding plate; an upper packing strip transport gap exists between the front part of the lower sliding plate and the upper sliding plate, the limit part is correspondingly positioned at a left side of the strip transport gap, the front part of the lower sliding plate is provided with a lower packing strip transport limit slot, a mouth of which is open toward a direction of the front part; a retaining part is disposed on the top of a position, on the machine core bracket, where the guide structure for guiding the left cutter, the middle cutter and the right cutter to move upward or downward is disposed, the retaining part is corresponding to the mouth of the limit slot, arid the strip transport gap is positioned at the mouth of the limit slot; the limit structure is configured to limit a movement distance of the lower sliding plate relative to the upper sliding plate, before the lower sliding plate slides backward from a position of an initial state thereof to a middle position, the limit structure does not obstruct the lower sliding plate to slide backward so that the upper sliding plate keeps in a position of an initial state; when the lower sliding plate slides backward from the middle position, the limit structure obstructs the lower sliding plate so that the upper sliding plate is driven to slide backward together with the lower sliding plate to an open state, the middle position is a position where the lower sliding plate is separated from the lower packing strap at the limit slot thereof; and a position of the ironing head in a left and right direction is corresponding to a position between the right cutter and the retaining part.