According to the characteristic of the higher Ca2+，Mg2+concentration in formation water and more acid sensibility mineral in reservoir rock of CO₂ flooding in Yanchang formation，the corrosion and precipitation simulation experiments of CO₂，formation water and rock mineral system in the different parts of reservoir was carried out. The results showed that the dissolution quantity of CO₂ increasesd gradually and pH value increased in formation water，precipitation wouldn’t happen due to pressure decreased in CaCl2-type formation water and corrosion reaction would happen between CO₂-water solution-reservoir mineral in the near-wellbore area of CO₂ injection well and deep area of reservoir. The dissolved CO₂ would escape form formation water largely，and the carbonated inorganic scale would generate in CaCl₂-type formation water and some mineral that dissolved in formation water would separate out largely due to the pressure decreases quickly in the near-wellbore area of production well. Therefore，precipitation would not happen easily and the physical properties of reservoir would be improved in the near-wellbore area of CO₂ injection well and deep area of reservoir；but carbonated inorganic scale would be precipitated easily and caused by reservoir blockage in the near-wellbore area of production well in Yanchang formation.