Abstract: The relationship of the microstructures and impact toughness of simulated welding Heat Affect Zone (HAZ) in 2205 Duplex Stainless Steel (DSS) were investigated by using material thermal simulator technique and others analyses methods.The effect rules of cooling time on the impact toughness of simulated HAZ were studied at the same time.The results show that the cooling time has strong influences on the impact toughness of the simulated HAZ,that the ferrite content decreases and precipitate of carbide and nitride in ferrite increases as increasing cooling time,that impact toughness increases with the increase of the cooling time t12/8 for a certain cooling time t8/5,and that that impact toughness decreases with the increase of the cooling time t8/5 for a certain cooling time t12/8.