Abstract: Ball head hanging rings are often susceptible to natural environmental influences, causing defects such as cracks and wear, which in turn affect the operation of transmission lines. To address this issue, ultrasonic detection technology of transmission line ball joint hanging ring based on ResNet50 was proposed. An ultrasonic detector was used to collect a large number of echo signals from the ball head hanging ring, and then a threshold function was used to smooth the collected echo signals. Under the influence of ResNet50, multiple convolutional layers were set up to extract multiple features of the echo signal. By setting a loss function, a ball head loop detection model was constructed. Based on this, the detection model was solved, the defect parameters of the ball head hanging ring were calculated, and the ultrasonic detection results of the ball head hanging ring were outputted. The experimental results showed that the designed ultrasonic detection technology had a false detection rate of 6.22% in practical applications, and the detection accuracy was relatively high.