Abstract: Synchrotron Radiation X-ray was performed on the anthracite coal sample from Sihe Mine in Qinshui Basin at beam energy of 24 keV, then CT slices of the sample were obtained by reconstructing the projections images. The CT slices of the sample were analyzed by adopting the methods of the digital terrain model (DTM) and the data-constrained modelling (DCM) respectively. The results showed that, as for the coal sample used in this paper, the porosity calculated by DTM was close to that measured by combination of the true density and the apparent relative density method. Yet, the porosity obtained by the threshold segmentation method based on the threshold determined by DTM was quite different from the porosity calculated by DTM. The porosity calculated by DCM was consistent with the porosity calculated by DTM and the experimental results. By taking the partial volume effect of the CT imaging process into considration, the DCM obtained the distribution information of pores whose size were smaller than that of the CT voxel size, which expanded the characterization length scale of CT imaging technique to some extent. The DCM calculated results indicated that most pores in the coal sample mostly coexisted as partially occupied CT voxels with coal matrix or mineral compositionsl.