Abstract: In order to improve inspection result repetition and flaw ration veracity of manual ultrasonic inspection of offshore platform structures, an ultrasonic phased array inspection imaging technology applied to offshore platform structure was proposed. A zone discrimination method is applied to divide weld into several vertical zones, and weld zones were swept by ultrasonic transducer perpendicular to weld, and inspection result was displayed in image. Inspection scheme of offshore platform structure ultrasonic phased array was also presented, and the reference block of offshore platform structure was detected by this system. Experiment results indicate that the method has the same inspecting capability as conventional ultrasonic inspection method, but the former is more excellent than the latter in repetition and reliability of inspection result, etc.