The stacking height of particles is indicative of the filling density of a packaging bag, where a higher stacking height corresponds to lower filling density and vice versa. The work aims to explore how different vibration parameters (vibration time, frequency, amplitude and direction) affect particle stacking height, so as to improve the filling density of the packaging bag. A PET particle accumulation model was established by EDEM numerical simulation software based on the Discrete Element Method (DEM). The accuracy of the model was validated through MATLAB image processing techniques and experimental verification. Simulations were conducted to assess particle accumulation behavior under both stationary and vibrating conditions. The vertical vibration effectively reduced particle stacking height and increased filling density. As vibration time increased, the stacking height decreased progressively and then stabilized, with a maximum reduction of about 17.70%. Increasing vibration frequency led to a significant decrease in stacking height, with a maximum reduction of approximately 16.67%. Reducing vibration amplitude resulted in a gradual decrease in stacking height, with a maximum reduction of around 18.59%. Thus, optimizing vibration parameters on the vibrating belt conveyor can significantly enhance the particle filling density in packaging bags.