The strength, performance, and application of carbon fiber reinforced plastic (CFRP) composites are directly affected by the interfacial bonding between fiber and resin. Wet winding technology is a commonly used composite productive process, and improving interfacial bonding of composites by on-line treatment has always been the focus of attention. In this paper, an on-line ultrasonic treatment system is designed and realized, the resin content of prepregs is determined by the dissolution method; standard deviation and dispersion coefficient are also calculated. The surface morphology, internal structure of prepregs, and the component of resin are observed and analyzed using a Metallurgical Microscope, scanning electron microscope (SEM), and near infrared radiation spectra (NIRS). The strength and performance of prepregs [(tensile strength, bending strength, tensile modulus of elasticity, bending modulus of elasticity, and interlaminar shear strength (ILSS)] are also tested. The results show the on-line ultrasonic treatment system can effectively improve the interfacial bonding of CFRP composites and enhance the strength and performance of CFRP composites.