Eight groups of ore samples with different particle sizes were scanned with X-ray computed tomography(CT)scanner and their cross-sectional images were obtained.Based on image analysis,the pore size distribution probability of each ore sample was calculated and fitted.The results show that the pore size of granular media appears a normal distribution.With the increasing of particle size of ore sample,the mean pore size increases.The mean pore diameter is positively and linearly correlated with seepage coefficient.With the increasing of mean pore size,the seepage coefficient increases when the other conditions keep constant.By CT technology together with image processing,the quantitative analysis of pore size distribution of granular media can be realized.