Abstract: Diagenesis of tight sandstone in Xishanyao Formation Baka aera is carried out by observing the core in the field and
identifying thin section as well as analyzing scanning electron microscope（SEM），X-ray diffraction and cathodoluminescence.
The results indicate that feldspathic litharenite and litharenite with low porosity and permeability are reservoirs in Xishanyao
Formation in Baka area under the environmental effect of braided river delta and lacustrine facies. Diagenesis is at mesogenetic A
stage，and its types involve compaction，cementation，dissolution with compaction as the most destructive effect and dissolution
as main constructive diagenesis.

Key words: Tuha Basin, Baka Area, Xishanyao Formation, tight sandstone, diagenesis