The invention relates to a prestressed steel strand anchor rod tensioning auxiliary device which comprises a pull rod, a pull rod nut, a front clamping box, a rear clamping box and a connection lock. The lower end of the pull rod is provided with a lower end head. The rear clamping box is provided with a clamping box screw rod and a clamping box nut matched with the clamping box screw rod. The front clamping box is provided with a screw rod hole. The front clamping box and the rear clamping box are buckled together through the clamping box screw rod, the screw rod hole and the clamping box nut to form a clamping box main body. The lower end head of the pull rod and the connection lock are placed in a clamping box cavity. The upper end of the connection lock is provided with a locking plate hole, a locking plate is placed in the locking plate hole, and an anchor rod hole is formed below the locking plate hole. The prestressed steel strand anchor rod tensioning auxiliary device has the beneficial effects that the problem that an exposed steel strand is short (not smaller than 20 cm) and difficult to tension and lock is solved through the pull rod, the front clamping box, the rear clamping box and the connection lock. By using the prestressed steel strand anchor rod tensioning auxiliary device, the length of a steel strand can be shortened in a design stage, the manufacturing cost can be reduced, and the problem that the exposed steel strand cannot reach the tensioning length can be solved emergently in the constriction process.