Abstract: The article describes the whole process of the Acoustic Emission detection of 1000m3 propylene spherical tank. Two acoustic emission sources were found during the detection process. The first one was between the first and second boost process and also was at the first pressure stable period for the ring weld BC30 ~ BC31. The second one appeared in the first and second boost process for D2 longitudinal weld. The source signals were analyzed by using the software and larger waveform differences between them were found. Ultrasound and radiographic testing was carried out and BC30~ BC31 weld cracks defect and D2 longitudinal weld defects of lack of fusion were found, thus confirming the feasibility of acoustic emission testing.