Abstract: This article describes the acoustic emission (AE) detection technology in high background noise environments. The AE technique was used for on-line detection and analysis of the reformed parts of a gasifier and the acoustic emission test results were re-inspected by conventional NDT methods. The results showed that acoustic emission testing technology could have good correspondence with conventional NDT methods in detecting the defects, which proved the feasibility and effectiveness of acoustic emission in high background noise. The results could provide reference for AE test of similar large-scale petrochemical equipment.