Tight oil is the most potential reservoir in the future. A large amount of EOR methods are developed to enhance the oil recovery in America and Canada, such as CO₂ EOR method, N₂ EOR method, solvent assisted method and water flooding. In this research, Yanchang oil field is selected as the research sample to compare N₂ replacing method and water flooding method. 12 experiments are completed and the experimental and simulation results indicate that N₂ has the better effect but it costs more.