Ultrasonic oscillation as a new polymer processing technology, was introduced into the polymer melt to improve the high melt strength Polypropylene (HMSPP) foaming ability, the effect of the ultrasonic oscillation power, Azodicarbonamide (AC) and talc content on the cell morphology, cell size, apparent density, cell density and nucleation density of the HMSPP foam was systematically studied. When the ultrasound and talc were introduced into the HMSPP melt, the HMSPP foam had a larger cell density and smaller the size as well as more uniform distribution. Interestingly, when the talc was introduced into the HMSPP, the cell morphologies changed from sphere to oval. Compared to the HMSPP foam without ultrasonic oscillation, the minimum thermal conductivity of the HMSPP foam with ultrasonic power 100 W reached 0.055 W/mK. When the talc was introduced into HMSPP melt, the average sound transmission loss value of the HMSPP foam were enhanced, and reached 30.37 dB, which was 13.7% higher than that of the HMSPP foam without talc and ultrasonic oscillation. The ultrasonic-assisted extrusion foaming had a promising to construct a new method to continuously and rapidly fabricate polymer foam with low thermal conductivity and excellent sound insulation properties. POLYM. ENG. SCI., 58:1678-1684, 2018. (c) 2017 Society of Plastics Engineers