Cable joints had an important connecting role in the cable system. Aging of the crosslinked polyethylene (XLPE)/silicone rubber (SiR) interface was the major cause of joint failures. Ultrasonic inspection is a safe and non-destructive means of inspection. In order to clarify the relationship between interfacial aging properties and ultrasonic characteristics, interfacial aging experiments were carried out. The aging properties of interfacial silicone rubber materials were tested and the changes in interfacial ultrasonic characteristics with aging were analyzed. The results shown the XLPE/SiR interface roughness increased with the interface aging, and the ultrasonic echo amplitude at the XLPE/SiR interface decreased due to the enhanced interfacial scattering. When the interfacial pressure increased, the interfacial contact area increased. Therefore, Ultrasonic transmission at the interface was enhanced. Higher interfacial pressures resulted in smaller changes in ultrasonic amplitude due to interfacial aging. The research has certain reference significance for the ultrasonic detection of cable joints XLPE/SiR interface aging.