Abstract: The 8th member of the Lower Permian Shihezi Formation occurs as important hydrocarbon reservoirs in eastern Sulige Gas Field, Ordos Basin. The secondary porosity and associated controlling factors of the hydrocarbon reservoirs are explored in detail on the basis of thin section examination, quantitative statistics, fluid inclusion thermometry and compositional analysis. The development of the secondary porosity in the 8th member of the Shihezi Formation is believed to be closely correlated to sedimentary microfacies distribution and organic acidic dissolution during the hydrocarbon generation and migration, and deep-seated hydrothermal fluids associated with the basement faulting. On the whole, the planar distribution of the secondary porosity is constrained by sedimentary facies, regional structures and hydrocarbon migration pathways. The secondary porosity tends to be best developed along the axial line of the nose uplift, or near the intersection of the distributary channels and the juncture of the basement faults.