Abstract: By using the advanced techniques of constant velocity mercury pressure and NMR fluid saturation testing, combined with conventional reservoir physical analysis, the characteristics of petrology, pore, porosity and permeability distribution of Yanchang Chang 6 sandstone reservoir in Ganguyi oil area, Ordos Basin have been systematically studied, and then the comprehensive classification and evaluation of Chang 6 reservoir in Ganguyi oil area have been made in this paper. The results show that the lithology of Chang 6 reservoir in Ganguyi oil area is dominated by fine feldspar sandstone. The reservoir space types mainly consist of residual intergranular pore and dissolution pore. The reservoir of Chang 6 reservoir in Ganguyi oil area is dominated by microlarynx, and the flow property of this reservoir is mainly controlled by the throat size. The saturation of movable fluid in the reservoir is on the low side. On the whole, the Chang 6 reservoir in Ganguyi oil area is characterized by low porosity and ultra-low permeability. The reservoir of Chang 6 reservoir in Ganguyi oil area has been evaluated by the geological parameters, such as storage coefficient, formation coefficient and flow zone index. It is considered that Chang 6 reservoir in Ganguyi oil area can be divided into 4 types, and the type Ⅲ with poor reservoir is the main reservoir.