Mobility at the surface of polymer matrix is crucial for enhancing the interfacial and overall performance of continuous fibre reinforced composites (CFRP). This study presents simulations in conjunction with experiments to reveal how ultrasonic vibration improves the activity of molecular chains and further enhances the performance of CFRP. Ultrasonic vibration could significantly improve the surface activity of molecular chains because of the superposed gradients in segmental dynamics and chain conformation. The improved mobility and activity advances the infiltration and interaction between polymer and fiber bundle and further strengthens the interfacial and overall performance of CFRP. The interlaminar shear strength and tensile strength of the specimen treated with 30W ultrasonic vibration can reach 26.41 MPa and 173.09 MPa respectively, 82.89% and 10.73% higher than the untreated specimen, which coincides with segmental dynamics of PLA chains and authenticates the effectiveness of ultrasonic vibration on improving the performance of CFRP by promoting matrix activity.