[Objective] Characterization of the shape, type and spatial distribution of pore-fissure structure in paleosol was conducted accurately in order to provide an important basis for the study of hydraulic properties of paleosol in slopes.[Methods] X-ray CT was used to scan the undisturbed samples of S₅ paleosol at southern tableland of Jingyang County, Shaanxi Province. Three-dimensional digital paleosol model was established through filtering, thresholding and reconstruction by using 3D visualization software including VG studio Max and AVIZO. The two and three dimensional porosity were calculated, pores and fissures in paleosol were extracted and classified based on shape factors, and the characterization algorithms for various voids were proposed.[Results] ① The pores and fissures coexisted in paleosol, which was of significant verticality and spatial heterogeneity in space. The voids could be differentiated by the shape factors (SFs) into fissures (SF > 40.18), branching pores (7.01 < SF ≤ 40.18), long columnar pores (2.0 < SF ≤ 7.01), ellipsoidal pores (1 < SF ≤ 2), and spherical pores (SF ≤ 1) on spatial pattern; ② the macroporosity (the equal diameter larger than 100 μm) is 9.86%, accounting for 23.94% of the total porosity (41.18%), indicating that the voids with equal diameter smaller than 100 μm are dominant in paleosol; ③ the pore size distribution is between 0.1~5 mm, in which the pores within 0.1~0.7 mm are in the majority on count, and the pores within 0.7~1.0 mm are in the majority of volume contribution rate, and the maximum fissure opening is 5.1 mm.[Conclusion] Paleosol is a kind of double-medium soil with majority of micro, small, medium pores as well as special large pores or macropores accompanying micro fissures or fractures. In addition, X-ray CT and 3D visualization reconstruction technology provides an effective method for the identification and characterization of pore-fissure structures in paleosol.