An introducer for being fitted with a circular stapler, is a flexible plastic member in a whole shape of conical with an inner cavity; the introducer has a proximal end (17) and a distal end (15), outer diameter of the introducer is gradually increased from the distal end (15) to the proximal end (17) and a maximum outer diameter of the proximal end is less than or equal to outer diameter of a staple cartridge (3) or a staple cylinder (1); when pulled by an external force, the plastic member is unwound spirally in a sequence from distal to proximal and finally forms a strip body capable of being disengaged from the circular stapler. The introducer provided by the present disclosure has the advantages that: as the maximum outer diameter of the introducer is approximately equal to the maximum outer diameter of the staple cartridge assembly, the process of introducing can be achieved without bad influence resulting from increasing the outer diameter of the circular stapler. Moreover, the introducer can be pulled out from the circular stapler in one piece in the form of a strip, so that the operation is convenient and no additional step can be added for the subsequent operation of the circular stapler.