By the physical property analysis, SEM, casting slice, and the technology of High pressure Hg injection, Superlow permeability sandstone samples in Yan25, Zhuang40, and Zhuang19 areas of the Yanchang Formation in Ordos basin were tested, in order to analyze the micropore structure. The research shows the heterogeneity is intense. The variety of pores and throats are main reasons that the permeability is low.When the sorting coefficient of pore throat is from 2.0 to 2.5 and the coefficient of variation is from 0.1 to 0.2, the reservoir quality is good. The coarse throat is the significant factor for the permeability, and the fine throat is significant to the storage volume. The microfracture is very good. The difference of quality, parameters of pore throat, and so on results of the micropore structure.