Abstract: Abstract: The MMA-g-BA-g-MMA (MBM) triblock copolymer was synthesized via RAFT emulsion polymerization and was blended with PVC. The plasticizing behavior and Dynamic mechanical properties were studied using torque rheometer and dynamic mechanical analyzer, and the mechanical properties were tested. The results indicate that MBM can efficiently reduce the plasticizing time and the balance torque; The blends show the best impact strength when the MBM content is 25 wt%, which is 3.0 times higher than neat PVC. As the MBM content increases, the storage modulus decreases to some extent, the tanδ peak value falls down and then rises and the Tg increases by about 5 oC to pure PVC. MBM can be used as processing and toughing aid for PVC.