The invention relates to the technical field of prefabricated part manufacturing for bridge tunnel construction. A cable wire tensioning mechanism for manufacturing a concrete prefabricated bridge plate comprises a cable wire reel supporting frame and a cable wire tensioning mechanism; the cable wire reel supporting frame comprises a supporting seat, protection cages and a rotary shaft located in the protection cages; the cable wire tensioning mechanism comprises a base, slide rails, pulling rods and driving cylinders, wherein the slide rails are arranged on the base, the pulling rods are slidably connected to the slide rails, and the driving cylinders drive the pulling rods to slide on the slide rails; cable wire pass holes extending in the extending directions of the slide rails are formed in the pulling rods, tapered face sections and tapered clamping heads matched with the tapered face sections are arranged at one ends of the cable wire pass holes, clamping through holes extending in the axial directions are formed in the tapered clamping heads, each tapered clamping head is spliced by at least two clamping blocks which are distributed in the circumferential direction of the tapered clamping head so as to enclose each clamping through hole, and mounting holes are formed in the base. The cable wire tensioning mechanism for manufacturing the concrete prefabricated bridge plate solves the problem that it is toilsome to tension the cable wire manually in the manufacturing process of the concrete prefabricated bridge plate.