A JKR-based dynamic model, with energy dissipation through both irreversible snap-on/snap-off process and viscoelastic effect, is developed to simulate the dynamics of low-velocity normal impact of micro-sized particle with a flat surface. The first-contact energy loss because of the incompletely reversible, quasi-static loading/unloading is incorporated in the dissipation model. The damping forces corresponding to both the attractive and repulsive components of the JKR contact forces are introduced to account for the hysteresis related to material viscoelasticity. The predicted particle behaviors for the impacts with incident velocities below or above the critical velocity are discussed. The predictions of both the critical velocity and the variation of restitution coefficient vs. incident velocity are compared with experiments in literature where reasonable agreement is obtained. The dependence of restitution coefficient on incident velocity is analyzed. Finally, the model sensitivity analysis such as the effect of the damping coefficient variation is discussed. The work provides a solid basis for the development of discrete-element-method approach of micro-sized particulate system.