Abstract: Polyethylene pipeline is widely used to transport high pressure gas in cities. The accelerated aging caused by the deterioration of service environment can lead to unexpected damage of the pipeline, which seriously affects the safety of people's lives and property. In this paper, a nonlinear ultrasonic detection method for PE pipe aging was proposed, and a nonlinear ultrasonic detection system for PE pipe flooding was constructed, and the detection parameters were optimized by test method. The characteristic parameters of nonlinear ultrasonic detection of pipes with different aging degrees were extracted, and the characteristic characterization model of nonlinear ultrasonic detection of pipes with different aging degrees was established. The results showed that a stable detection signal can be received by adjusting the water distance properly, and the nonlinear ultrasonic detection coefficient increases significantly with the increased of aging degree, which can be used to form a nonlinear characterization model of aging degree, which can be used for non destructive testing of thermal oxygen aging of PE pipes.