The acoustic emission（AE） detection system was established to test a 125 000 m3 external floating roof tank at a branch of SINOPEC Corp.After the acoustic emission signals were collected, waveform and parameters analysis were carried out to get the key features.Then cluster analysis was used to study the corrosion situation of the tank floor.Last, the magnetic flux leakage inspection results were adopted to evaluate the reliability of AE technology on tank testing.The results show that the acoustic emission detection technology is an ideal method for inservice atmospheric storage tank for its good economic efficiency, high reliability and low time cost.