The utility model discloses a CO2 welding wire feeder. The CO2 welding wire feeder comprises a driving transmission wheel which is coaxially and fixedly connected with a transmission shaft of a motor, two auxiliary transmission wheels are respectively and synchronously connected with the driving transmission wheel in a meshed transmission mode, the two auxiliary transmission wheels are respectively and fixedly connected with a lower pressing wheel in a coaxial mode, and the two lower pressing wheels correspond to two upper pressing wheels. The CO2 welding wire feeder effectively solves the problems that single wire feeding is unstable and wires are blocked in the process of wire feeding, the work load that a worker replaces contact tubes and unblocks conduits repeatedly in the process of production is reduced, the number of the contact tubes is reduced, the number of welded joints caused by wire blocking is reduced, and the production efficiency and the appearance quality of products are improved.