Abstract: The corrosion and even perforation of tank bottom have seriously threatened the operation safety of tanks. In this paper, the pitting corrosion behaviour of the specimens of Q235 plate steel used for atmospheric storage tank bottom in acidic NaCl solution (mass fraction is 3%, pH is 2) was studied by acoustic emission (AE) and electrochemical technologies. The distribution of characteristic parameters of AE signal (including amplitude, energy, hits, duration time and rise time) over the time in each stage of pitting corrosion, and the relationships among them were analyzed. In addition, the AE monitoring results were compared with the electrochemical polarization results. It is shown that the AE monitoring results are consistent with the electrochemical polarization results during the pitting corrosion of bottom plate steel, the AE signal characteristics are remarkably different in the exfoliation and rupture of oxide film, the formation and propagation of corrosion pit, the friction between corrosion products and the cracking behaviour, and the extraction of these characteristics is helpful for assessing the AE on-line detection results of the bottom of atmospheric metal storage tank, diagnosing the corrosion degree and identifying the corrosion type.