Abstract: In view of the characteristics of strong penetration and extremely sensitive to delamination of materials, ultrasonic wave has unique advantages in coating defect detection. In order to quickly and accurately detect the defects of the outer coating of submarine oil and gas pipelines, and make up for the weakness of the existing coating detection technologies for oil and gas pipeline, such as low reliability, vulnerable to external interference, inaccurate positioning, etc., a pipeline coating defect detection method using ultrasonic pulse echo was proposed. Through ANSYS modeling and simulation calculation, the attenuation characteristics of reflected echo between intact coating interface and defective coating interface were compared, and obvious differences can be seen in the amplitude of echo after multiple reflections. The fifth echo signal was selected as the basis for determining the coating defects, and the reliability of simulation results was verified by designed test. This study shows that the method has high sensitivity to accurately detect coating defects. The operation is simple and reliable, not affected by the submarine complex environment, and meets the needs of continuous detection, so it can guarantee the safe and efficient operation of submarine oil and gas pipelines.