Rape stalk was synergistically pretreated by alkali and ultrasound and prepared rape stalk/PVC composites. The properties of composites were examined and the results showed that the composites synergistically treated by alkali and ultrasound demonstrated considerably increased in hardness, mechanical strength, thermal stability and wear resistance. Compare to composites treated with ultrasound, the hardness, tensile, impact and flexural strength of synergistically treated composites were increased by 7.74 %, 8.32 %, 10.34 %, 13.80 %, respectively. Compared to composites treated with alkali, the increases were 6.48 %, 4.35 %, 1.59 %, 2.10 %, respectively. In addition, compared to composites treated with ultrasound, the best wear resistance of composites after the synergistic alkali-ultrasound treatment was achieved which showed decreases in wear loss and specific wear rate of 11.96 % and 14.46 %, respectively. Reductions of 9.48 % and 8.43 %, respectively, were obtained in comparison to composites treated with alkali. Therefore, the synergistic alkali-ultrasound treatment is potential to improve the properties of composites.