The invention provides an interfacial shear stress measurement device for a pre-stressed anchor. The device comprises a rod body, a PVC pipe which is arranged above the rod body and parallel to the rod body and is used for importing lead wires, at least one PVC pipe ring which is connected with the PVC pipe and is alternately embedded outside the rod body; rectangular slots are respectively formedin two sides of the PVC pipe ring; the rod body comprises an inner anchoring section extending into surrounding rock and a free section extending out of the surrounding rock; strain gauges I are respectively adhered to two sides of the rod body corresponding to the position of each PVC pipe ring, and a fine steel bar is hinged in the position; the strain gauges I are distributed on the inner anchoring section according to testing requirement; strain bricks adhered with strain gauges II are respectively drawn out by the fine steel bar toward two sides of the rod body, and the strain gauges IIface to a to-be-measured interface; preserved holes for lead wires to penetrate are formed in the position, contacted with the PVC pipe, of the PVC pipe ring; and an external deformeter is connected with the strain gauges I and the strain gauges II respectively through lead wires. The device facilitates better studying of the long-term safety and durability of a rock soil prestressed anchoring structure.