Abstract: The long service time and the strong corrosive media of steel atmospheric storage tanks in oilfields result in serious internal corrosion, so there is a huge security risk. In order to confirm the seriously corroded positions and guide the maintenance and anti-corrosion operations of storage tanks, it is in urgent need to detect the internal corrosion of steel atmospheric storage tanks. In this paper, the on-line detection device with internal corrosion coupon in steel atmospheric storage tanks was developed. The corrosion detection at oil-water interface and oil-gas interface of storage tanks was realized by using the float coupon. In addition, the corrosion detection in sludge phase, sewage phase, oil phase and gas phase was achieved by using the rigid coupon. What's more, the assembling of detection device and the qualitative continuous characterization of corrosion degree at different heights of the storage tank were realized by using the thread-connected rodlike hollow joint lever whose material is the same as that of the storage tank to be detected. Thus, the on-line detection of corrosion rate at six phases in the same storage tank was innovatively achieved. It is shown that the reproducibility of the detected corrosion rates in two cycles is over 91% and the corrosion rate detected by the coupons is coincident with that calculated from two detection results by the ultrasonic wall thickness detector in the same tank. It is demonstrated that the detection result is stable and reliable. By virtue of the detection device with internal corrosion coupon in steel atmospheric storage tank, the key internal corrosion positions of the storage tank can be determined and the hidden corrosion dangers can be identified in time, so as to provide the guidance for the maintenance, replacement and targeted corrosion control of the storage tanks.