A new method using high intensity ultrasonic wave has been developed for the degradation of polymer melt in an intensive mixer. For the effective transfer of ultrasonic energy, experimental apparatus was specially designed so that polymer melt can be in direct contact with the ultrasonic horn. In this research, we observed that the significant degradation of polypropylene (PP) melt in a mixer occurs due to the action of ultrasonic wave without any aid of additives or solvents. To compare the degradation efficiency of ultrasonic irradiation with that of peroxide, additional experiments were performed to practice the peroxide-aided degradation by mixing I part of dicumyl peroxide with PP in the mixer. It was also found that the direct sonication on polymer mixture in melt state reduces the domain sizes and stabilizes the phase morphology of the blend. It is suggested that ultrasound assisted melt mixing can lead to in situ copolymer formation between the components and consequently provide an effective route to compatibilize immiscible polymer blends.