The utility model provides a chain drive straining device of yarn woven machine, it is including rack -mounted drive chain and drive drive chain moving sprocket, the last tensioning assembly that is equipped with of drive chain, tensioning assembly including U -shaped spare, jib, hanging wheel, wherein, install in U -shaped spare bottom at the jib top, the meshing of jib bottom has butterfly nut,overlaps on the jib between butterfly nut and the U -shaped spare and is equipped with the balancing weight, the hanging wheel both sides are equipped with the shaft to through shaft movable mountingin U -shaped spare, the hanging wheel wheel face is equipped with the U -shaped spacing groove of indent, spacing groove tank bottom department is equipped with tooth, drive chain is located limitinggroove, and meshes with tooth. Chain tensioning after this scheme of adoption is effectual, the operation is stable, the practicality is strong.