Abstract: High-nitrogen austenitic stainless steel (HNS) that has good properties is a kind of structural steel alloyed with the nitrogen replacing nickel. The properties of the welded joint can affect the application of HNS, so the welding technique is considered as one of the key techniques for its applicntion. In order to study the welding technique of HNS, the microstructure and hardness of heat affected zone (HAZ) of HNS were investigated by simulation on a Gleeble-1500 thermal simulator. The experimental results indicate that the microstructure in the HAZ of HNS is austenite and δ-ferrite. Under the experimental conditions, the amount of the δ-ferrite increases when the cooling rate increase, and it increases while the staying time at the peak temperature increases. The results also show that the hardness of the HAZ is higher than that of the base metal, indicating no softening of the HAZ under appropriate welding conditions.