The invention discloses a road construction barrier prefabricating device. The device comprises a mounting base, wherein servo motors are fixed to the two sides of the upper end face of the mounting base, the ends of output shafts of the two servo motors are in key connection with first chain wheels, the two sides of each first chain wheel are in transmission connection with second chain wheels through chains, lead screws are fixed to the two second chain wheels, the sides, close to the second chain wheels, of the lead screws are rotationally connected with supporting plates through bearings,the supporting plates are fixed to the mounting base, the ends, away from the supporting plates, of the lead screws are rotationally connected with supporting blocks through bearings, the supporting blocks are fixed to the middles of the two sides of the upper end face of the mounting base, the two lead screws are in threaded transmission connection with moving blocks, a first forming die and a second forming die are symmetrically fixed between the two sets of moving blocks, a vibration motor is fixed to the middle of the lower end face of the mounting base through bolts, vibration mechanismsare arranged at the four corners of the lower end face of the mounting base, automatic die assembling and disassembling are achieved, the vibrating function is achieved, and the product quality is improved.