Since the mechanical failure of granular soils is the macro-manifestation of complex internal particle interactions, studying this relevant issue from micro-scale perspective is of fundamental importance. Acoustic Emission (AE) has become a promising approach for this purpose; however, its synthetic and validating study on granular soils with various ground conditions is far from substantive. In an attempt to verify and correlate the relationship between AE behaviors and mechanical behaviors of granular soils with various conditions, results of drained triaxial compression tests along with AE measurements recorded during testing are discussed. These results revealed intrinsically different propagation properties of acoustic waves between saturated and unsaturated/dry sands. The water in saturated sands facilitates acoustic waves to propagate with less attenuation, whereas discontinuities (i.e. particle-particle contacts and particle interfaces with water) in dry/unsaturated sands lead acoustic waves to propagate with larger attenuation. The AE manifestation showed its high sensitivity to different saturation degrees, package densities and confining stress levels, which allows the evaluation of ground conditions to be made by AE. The congruous AE evolution in saturated sands was considered closely related to particle interactions during drained triaxial compression; whereas the changeable AE evolutions in accordance with different failure patterns in dry sands were considered relating to soil structure behaviors.