Abstract: Taking the oblique defect of steel pipe detected by phased array probe as an example, the definition of oblique defect, the technical characteristics of phased array probe and the adaptability of phased array probe to detect oblique internal defect and external defect were analyzed, the corresponding model was established and the pipe sample was manufactured for oblique defect detection test. The experimental results show that the phased-array probe bias method can be used to detect the oblique internal and external defects of the general seamless pipe (the ratio of diameter to thickness is greater than 5). This conclusion can provide some theoretical basis for the design and selection of phased array probe in the steel tube oblique defect detection process, and can also provide reference for the design and selection of other similar phased array probes.