Polymer-based anisotropic conductive film has become widely used in many electronic packaging interconnect applications. In this study, thermosonic flip chip bonding technology for anisotropic conductive film (ACF) joints of chip-on-glass (COG) assembly is investigated. The effects of ultrasonic power on the curing degree and bonding strength of anisotropic conductive film joints are discussed. The results show that (1) The bonding strength of the ACF joints firstly increases and then fast decreases when the ultrasonic power is continuously increased; (2) The curing degree of ACF material increases with the increase of the ultrasonic power. When the ultrasonic power is 3.52W, the curing degree of ACF material can reach 94.1%; (3) The optimized value of ultrasonic power is 3.5W for the studied assembly.