The invention relates to a modified cutter gate system of a microwave expanded tobacco stem cutting machine and belongs to the field of tobacco machinery. The modified cutter gate system of the microwave expanded tobacco stem cutting machine is particularly suitable for cutting microwave expanded tobacco stems. The modified cutter gate system of the microwave expanded tobacco stem cutting machine comprises an upper cutter gate, an upper cutter gate seat, a lower cutter gate, a lower cutter gate seat, a left cutter gate and a right cutter gate, wherein the upper cutter gate is connected with the upper cutter gate seat through screws, the lower cutter gate is connected with the lower cutter gate seat (5) through safety bolts, the upper cutter gate and the upper cutter gate seat are installed on a guiding arm of an outlet roller supporting shaft of an upper row chain, the guiding arm (12) synchronously move along with the upper row chain and can exert certain pressure on tobacco stem materials to be cut, and the lower cutter gate, the lower cutter gate seat, the left cutter gate fixed on a left wall board, the right cutter gate fixed on the right wall board, and the upper cutter gate and the upper cutter gate seat which can move clamp materials which are conveyed from the upper row chain and ready to be cut together. According to the modified cutter gate system of the microwave expanded tobacco stem cutting machine, movement is conducted on a cutter gate system of a KTC80E type leaf shredding machine, and slicing and shredding requirements of the expanded stems are met through narrowing of the range of the heights of the cutter gates and transformation of the size of each part of the related cutter gates.