Particle packing is widely applied in organic pollutant adsorption,catalytic reaction,biomass combustion,nuclear cooling,and other scenarios.Due to the complexity of the shape,the studies on the void frac-tion of the cylindrical particles are not as thorough as the spherical particles.This study investigated the influence of the filling rate,material properties and sphericity on the void fraction of cylinders through experiments and simulation.DEM (discrete element method) was validated by the internal structures of the packing obtained by CT (computed tomography).Based on the logarithmic correlation between the void fraction and filling rate,an ingenious framework for predicting the void fraction of cylindrical parti-cles was presented with two intermediate coefficients.By correlating the coefficients with the material property and sphericity,a novel void-fraction prediction model was established with R-squared of 0.996.The mechanism of void fraction under random loose packing for cylinders was eventually found in this study.