The invention belongs to the technical field of construction machinery equipment, and particularly relates to a precast concrete unit reinforcing steel bar binding machine which comprises a body framemechanism, a reinforcing steel bar grabbing mechanism, a reinforcing steel bar conveying mechanism and a full-automatic binding mechanism. The body frame mechanism comprises transverse beams, a thinrod, a thick rod, transverse beam auxiliary wheel parts, longitudinal beams, longitudinal beam connecting plates, longitudinal beam driving parts, a transverse beam lead screw, a screw nut, a transverse beam lead screw motor and supporting rods. The reinforcing steel bar grabbing mechanism comprises a mechanical arm base, a worm gear case, a worm motor, a mechanical arm, a driving cylinder and a mechanical claw. The reinforcing steel bar conveying mechanism comprises a reinforcing mesh binding platform, conveying supporting frames, long reinforcing steel bar conveying rails, short reinforcingsteel bar conveying rails, long wheel motors and long wheels. The precast concrete unit reinforcing steel bar binding machine is high in automation degree and binding quality.