The sandstone of Badaowan Formation developed in Kekeya structure of Taibei Sag under braided delta is mainly composed offeldspathic lithie sandstone and lithic sandstone．By means of thin slices，cast section and scanning electron microscopy observation as well as X-ray diffraction analysis，the petrologic characteristics，diagenesis stage division，diagenesis type and the influence on pore of Badaowan Formation aye studied．The results show that the sandstone developed in study area is in late diagenesis A2 stage，and experienced compaction，chlorite formation，quartz secondary enlargement，calcite precipitation，cementation and feldspar denudation．Compaction and cementation aye the main destructive diagenesis，while denudation is the main constructive diagenesis．Especially，the feldspar denudation is the significant factors favorable for reservoir．