Abstract: An automatic scanning equipment for ultrasonic testing of small-diameter tube welds was developed to solve the problems of large amount of work and uninspected weld zones due to the small gaps of the tube lines of power station water-cooling system in manual ultrasonic testing. All the welds in a boiler were automatically inspected by the probe scanning in the tube lines with gaps of ≥15 mm without missing. It was shown by on-site inspection that the equipment was effectual.