Abstract: Tight reservoir has become a hot spot of oil and gas exploration and development, meanwhile the study of pore structure is the core of the study of tight reservoir. Pore structure has a direct impact on the permeability of the reservoir. According to all kinds of pressure mercury parameters and permeability in correlation to determine pore throat size is the decisive factor of the reservoir permeability size, pore throat sorting and connectivity on the permeability of the influence is relatively weak.