Abstract: In the process of offshore oil and gas platform construction, phased array ultrasonic testing technology has been widely used in pipeline butt weld testing. According to the design requirements, the defects detected by phased array ultrasonic testing shall be evaluated according to Appendix R of ASME B31. 3-2020 “Process Piping”. The standard requires that the height and length of defects shall be measured during acceptance. However, the accuracy and reliability of phased array height measurement are not ideal. Through the study of phased array ultrasonic testing parameters such as acoustic beam focusing depth, probe angle and inspection sound path, the main influencing factors of defect height measurement in PAUT testing of carbon steel materials are analyzed.