The invention belongs to the technical field of tobacco manufacturing and particularly relates to a microwave tobacco stem expansion technology. The method comprises the following steps of preparation of raw materials, quantitative feeding, temperature raising of tobacco stems, microwave expansion, microwave dehumidification, cooling shaping and production of cut stems. The method has the advantages that the production cost is low, the structure is stable, the cut stems do not retract when absorbing water and can be directly produced without ageing treatment, the seamless joining between specialized, large-scaled and continuous processing of microwave expansion tobacco stems and production of cut tobacco is realized, the cycle of producing, storing and preparing cut tobacco is unnecessary, the logistics and warehousing cost during the ageing period of expanded tobacco stems is unnecessary, and the economic benefits are quite obvious.