The invention discloses a yarn tension mechanism which comprises a rack. A first tension disc and a second tension disc are arranged on the rack. The yarn tension mechanism is characterized in that a first coaxial central spindle set is arranged on the first tension disc; a second coaxial central spindle set is arranged on the second tension disc; the first coaxial central spindle set is provided with a first small central spindle and a first large central spindle which are different in radius; the second coaxial central spindle set is provided with a second small central spindle and a second large central spindle which are different in radius; and yarn sequentially passes through the first coaxial central spindle set and the second coaxial central spindle set and then flows to an outlet of the rack. The yarn sequentially passes through the first coaxial central spindle set and the second coaxial central spindle set and then flows to the outlet of the rack, the yarn passes through the different specific central spindles so as to generate different degrees of yarn tension, the yarn tension can be adjusted conveniently according to different requirements, the structure is simple, and adjustment is convenient; and in addition, an annular groove has a good limiting effect, so that the position of the yarn is prevented from deviating.