Abstract: The ultrasonic vibration was added to extrusion process, and the influences of ultrasonic vibration on the morphology, crystallization, electrical and thermal properties of nano graphene nanoplatelet (GNP)/polypropylene(PP) composites with high GNP contents were investigated. The results show that the ultrasonic vibration provides powerful shock wave and micro jet which can reduce the thickness of GNP effectively, reduce the agglomeration of GNP and enhance the uniform dispersion of GNP in PP matrix. The morphology is benefit for the building of electrical and thermal network, therefore the electrical conductivity and thermal conductivity of GNP/PP composites are increased. Compared to non-ultrasonic vibration, after the addition of 100 W ultrasonic vibration, with the increase of the GNP content, the amplitude of electrical and thermal conductivity improvement increase continuously, when the GNP content is 15wt%, the increase of electrical conductivity is 85%, and thermal conductivity is 9.7%. When the GNP content is 12wt%, with increasing the ultrasonic power, the electrical and thermal conductivity increase first and then decrease. When the ultrasonic power is 200 W, the increasement of electrical and thermal conductivity is 214% and 17.2%, respectively. While the results of 300 W ultrasonic treatment show that the higher power of the ultrasonic vibration makes the flake sizes of GNP decreased, which lets it more difficult to build a complete electrical and thermal network, so that the performance is slightly decreased.