A rotary cutter head for a surgical stapling instrument includes a staple cartridge, an annular cutter, a staple-pushing seat and a staple chamber. The staple-pushing seat and the annular cutter are connected by a bearing structure and provided with guide projections. The inner wall of the staple cartridge or the outboard of the expand-stopping tube is integral injection molded with a metal cylinder insert, on which is provided with a forward helix track and a backward track mutually independent and communicated with each other. The guide projections are mated with the two guide tracks and guiding the annular cutter to move along a helical path.
