Abstract: To conduct rapid and efficient corrosion detection of the grounding round steel of power transmission towers, a method based on ultrasonic guided waves for detecting corrosion defects is proposed. Firstly, suitable ultrasonic guided wave modes and frequencies for grounding round steel are determined through numerical analysis. Secondly, simulation models are established to analyze the propagation of L(0,1) ultrasonic guided waves in round steel with or without corrosion defects and investigate their effects. The results indicate that the amplitude of the defect echo is positively correlated with the depth and radius of circular hole corrosion defects, but has little correlation with the length of axial corrosion defects. Finally, experiments are conducted. Both simulation and experimental findings demonstrate that the L(0,1) ultrasonic guided wave method can effectively detect grounding round steel of transmission towers by quickly locating and quantitatively analyzing corrosion defects thereby improving detection efficiency. This method offers a new approach for detecting corrosion defects in grounding round steel used in transmission towers.