Reservoir sandstones of the Permian lower Shihezi formation in Daniudi gas field of Ordos basin, mainly consist of lithic quartz sandstone and litharenite, with low compositional maturity and median-high textural maturity. It belongs to extra-low porosity and permeability reservoir, with dissolved intergranular pores as the chief accumulation space. The lower Shihezi formation reservoir sandstones are now in the B stage of mesodiagenesis, the main diagenesis of which includes compaction, cementation, dissolution and replacement. The mechanical compaction, which principally takes place in the early time of burial history, is the predominant reason for reservoir quality destruction of lower Shihezi formation sandstones with burial depth shallower than 2 350 m. The different cementation and dissolution take place progressively with the burial depth increasing, making the destruction degree resulted by mechanical compaction weakened. The destruction impact of cementation is characterized by precipitation of different cement in primary and secondary pores. The cementation of pore-lining chlorite and carbonate exert two different influences on reservoir quality. The construction influence of pore-lining chlorite cementation on lower Shihezi formation reservoir quality is prior to destruction. The pore-lining chlorite can preserve some primary intergrannular porosity by weakening the degree of mechanical compaction and inhibiting the subsequent generation of quartz cement, furthermore, provide the passageway for the entrance of acid fluid of the A stage of mesodiagenesis and flowout of dissolved resultant product, making a large number of secondary pores produced. On the one hand, for the cementation of early stage carbonate, it not only weakens the destruction degree of mechanical compaction, but also provides favourable condition for the late disslotion; on the other hand, for the cementation of late stage carbonate, it precipitates in the pores and obstructs the throats, making the reservoir quality destructed heavily. Dissolution of the reservoir sandstones is the main factor of the development of secondary pores, which can improve the physical property of the reservoir sandstones. There are three dissolution zones in the lower Shihezi formation sandstones, located in the vicinity of 2 400 m, 2 500 m and 2 670 m perspectively.