Abstract: Polyethylene pipeline is widely used in urban high pressure gas transportation. Accelerated aging caused by deteriorating service environment can lead to unexpected damage of pipeline, which seriously affects urban production and life. In this paper, the nonlinear ultrasonic detection technology of PE pipeline and its fusion welding seam aging is proposed. The special nonlinear ultrasonic detection method is designed and the test system is constructed. With the proposed approach, the characteristic parameters of nonlinear ultrasonic detection of pipes and welds before and after accelerated aging were extracted, and the characterization performance of each characteristic parameter for pipes and welds was evaluated. The results show that the complexity and local difference of the microstructure and geometry of the weld lead to the large fluctuation of the characteristic parameters of ultrasonic testing when characterizing the aging of the weld, and the fluctuation influence is reduced by taking the average value of multiple tests. Although the fundamental amplitude and the second harmonic amplitude of pipes and welds decrease after aging, the nonlinear ultrasonic testing coefficients of fusion welded joints and pipes after aging increase by 156.5% and 132.1%, respectively, and the standard deviations of nonlinear coefficients increase by 157.1% and 81.3%, respectively.Therefore, the nonlinear ultrasonic testing technology is expected to be used in the nondestructive testing of pipes after thermal oxidative aging.