Non-obstructive Particle Damping (NOPD) is widely used as an effective passive damping technique. However, the understanding of the energy dissipation mechanism and meso-scale behavior of the granular system in NOPD is not sufficiently in-depth. In this paper, the damping effectiveness of NOPD, as represented by the contour plot of the loss factor, wds analyzed in combination with the motion modes of the granular system, and the energy dissipation mechanism was illustrated at the meso-scale. The results show that the different motion modes of rheology behaviors and meso-structure contribute to the variations in the damping effectiveness. Generally, the NOPD has the optimal damping effectiveness in the buoyancy convection state. The purpose of this paper is to provide a better understanding and theory support for the design and application of NOPD. (C) 2017 Elsevier B.V. All rights reserved.