To provide a yarn feed mechanism capable of surely holding the tip of a knitting yarn in carrying out a yarn changeover for a circular knitting machine.

This yarn feed mechanism works as follows: an air jet nozzle 13 is made to communicate with a small hole 11b provided on the tip of a yarn guide 10, and when a yarn changeover is to be performed, particularly in cutting an elastic yarn (b) with a ring cutter 43 and a cutter blade 44, compressed air is fed from a hose 16 and a pipe 14 and jetted through the nozzle 13, the yarn (b) is overfed to absorb the extension thereof, and the tip of the yarn (b) is surely held with a brush 41 and a suction port 42.