The current study is application of an acoustic emission sensing technique in fatigue damage measurement. It focuses on fatigue damage of the below-threshold cycles when they are excited by overloads. Acoustic emission (AE) is monitored while cracks are propagating. Some studies are carried out to reduce and isolate noises from the fatigue acoustic emission signal. Results shows that below-threshold cycles do cause fatigue damage measured by acoustic emission activities under the variable-amplitude loading condition. Acoustic emission signals from fatigue propagation are of an intermittent nature.