To explore modification effects of ultrasonic treatment on high-methoxyl pectin (HMP), HMP was used as raw material and processed by ultrasonic treatment under different powers (120, 240, 360 and 480 W). Rheological properties of HMP gel were tested. Moreover, the HMP gel formation process was analyzed through kinetic analysis. Results demonstrate that the viscosity of HMP was reduced significantly by ultrasonic treatment However, the rheological properties of HMP gel were retained, and they still showed typical pseudoplastic and shear thinning properties. HMP gel of the low-power treatment group showed better viscoelasticity compared with those of the contrast group. The maximum G' and G '' were achieved after HMP was treated by 120 W ultrasonic power when elasticity of HMP was enhanced significantly. Moreover, the structure of HMP was damaged by the cavitation effect and mechanical effect as ultrasonic power increased, thereby the strength of gel decreased significantly. Ultrasonic treatment could weaken the gel formation ability of HMP. During gel formation, the activation energy difference between the high-temperature and low-temperature stages reduced with increasing ultrasonic power. The 120 W treatment group achieved the maximum activation energy difference between the high-temperature and low-temperature stages, while the 480 W treatment group achieved the minimum activation energy difference. (C) 2018 Elsevier Ltd. All rights reserved.