In order to clarify the detection range of acoustic emission technology for the tank bottom plate inspection, the attenuation characteristics of AE signal from lead-break on the tank bottom plate are investigated in this work. First the attenuation of AE signals from the lead-break on the upper surface of the tank bottom plate and that from the lead-break on the lower surface of the tank bottom plate are studied and compared when the tank is empty, which indicates that the upper surface corrosion of the tank bottom plate is much easier to detect than the lower surface corrosion. The weld perpendicular to the AE transport direction contributed much to the attenuation of the AE signals from tank floor. Then, the influence of liquid level on the attenuation and transport path of AE signals from tank bottom plate are investigated when water is added into the tank with a level of 10cm and 70cm, respectively. The liquid changes both the attenuation trend and the transport path of AE signals.