Abstract: In order to realize the on-line monitoring of pipeline corrosion of oil and gas wellhead equipment, aiming at the key problems such as piezoelectric ultrasonic coupling, sensor installation, signal transmission and storage analysis, a cloud platform-based online monitoring system of pipeline corrosion is proposed. A new kind of couplant is developed for liquid-solid transformation, ensuring the good coupling effect. Then, the method of optimal node, positioning and fixation of sensor is studied. Besides, a B/S (Browser/Server) architecture based on cloud platform is proposed to storage and analyze the corrosion data. Finally, a multi-channel monitoring system of pipeline corrosion is developed. After nearly one year's outdoor test, the results prove that the system is stable and reliable, and all indicators meet the requirements of pipeline corrosion monitoring, laying a foundation for intelligent operation and maintenance of oil and gas wellhead equipment.