Yanchang Oilfield has rich reserves of low permeability reservoirs，but the conventional waterflooding development of these reservoirs shows the poor performance and the low oil recovery due to the tight reservoir matrix and the complex fracture systems. Therefore，it is urgent to enhance oil recovery in Yanchang Oilfield. In this paper，a new theory of “corrosion increasing permeability，wetting promoting permeability”was proposed for CO2 immiscible flooding in low permeability reservoirs base on the technologies and the field practices of the integrated CO2 immiscible flooding and sequestration，the air foam flooding at low temperature，the bioactive combination flooding and the microbial flooding. A CO2 immiscible flooding technology was developed to mainly improve CO2 miscibility and enhance 3D equilibrium producing of CO2 flooding. Moreover，the complex oxygen consumption mechanism in shallow reservoirs with a low temperature was revealed，and the formula systems of the air foam，the bioactive agents，and the endogenous microbial activators were improved. The field practices indicated that the prospect of enhanced oil recovery technology for low permeability oil reservoirs is broad in Yanchang Oilfield.