The present study focuses on providing enhanced monitoring methods to control balsa cored sandwich composites structures used in naval and construction industry. Some authors [1-2] have proven that moisture absorption can accelerate composite damages such as resin cracking, skin delamination and skin-core debonding. However, most related studies are via traditional mechanical tests, where it is difficult to know the initiation and the propagation of the damages in details. Recently, Acoustic Emission (AE) technique became a non-destructive tool to monitor the internal composite material changes by radiation and propagation of acoustic wave.In this work, we demonstrate that AE wave velocity and amplitude attenuation property can be useful parameters to reflect the variation of moisture content and stiffness of a sandwich structure.