Structure of selecting mechanism for circular knitting machines

A selecting mechanism for a circular knitting machine, comprising a hollow base, a plurality of selection units arranged in a stack within said hollow base, each selection unit comprising two parallel selecting jacks, and a selecting jack pushing-up device fastened to said hollow base and selected to set said selecting jacks into an operative or non-operative position for a full-stitch, half-stitch, or plain-stitch operation, wherein said selecting jack pushing-up device comprises a plurality of horizontal grooves corresponding to said selection units, a plurality of pairs of pivotally mounted pushing-up plates respectively and bilaterally mounted in said horizontal grooves, each pushing-up plate having a nose portion, which when pivoted between a first position and a second position, moves the respective selecting jack to the operative or the operative position, and a second position, in which the respective selecting jack is moved to the non-operative position.