Composition segregation and microstructure nonuniform of H13 steel have been obviously improved though adding nitrogen element. The microstructure and property of H13 steel with nitrogen contents of 0, 0.021%, 0.058% and 0.085% are studied under various quenching and tempering states. Dual quenching that is quenching between 1000~1010°C twice is employed in order to increase the tensile strength and hardness of coupons. The temperature and time are explored for improving the toughness under optimal quenching treatment. For extruding die steel, the tensile strength can reach a satisfactory level and impact toughness are met the requirements of NADCA at the temperature.