Abstract: By using cathode-luminescence,SEM,x-ray diffraction,casting thin section and intrusive mercury,the diagenetic evolution sequence,stage and micro-pore characteristics of Chang 6 reservoir in R area of Ordos Basin was discussed.The results show the main lithology is feldspathic sandstone and it mainly experienced compaction,cementation and dissolution.The cementation made an obvious damage on reservoir property,which was the main reason for reservoir density.Combined with sedimentary environment and pore characteristics,digenesis was divided into 5 diagenetic facies.Primary and secondary pore were mixedly developed,the average porosity is 6.71% and average permeability is 0.46 ×10~(-3)μm~2.This reservoir has strong heterogeneity and it belongs to low porosity and low permeability.In process of pore evolution,mechanical compaction and cementation play a destructive role in reservoir physical properties,while the solution can improve the physical properties.