To meet market demands for steel materials featuring high polishability， superior corrosion resistance and excellent strength-toughness balance， a high-quality corrosion-resistant plastic die steel with improved comprehensive properties is developed via optimizing chemical composition and heat treatment processes. The steel was smelted by the process route of "electric arc furnace + vacuum refining + electroslag remelting"， and large flat steel with a cross-sectional dimension of 230 mm×710 mm was manufactured using a 35MN rapid forging press. The effect of different post-forging heat treatment processes on the microstructure and properties of a novel corrosion-resistant plastic die steel 3Cr13NiMoVN was studied using JMatPro software， OM， SEM， hardness tester and impact testing machine. The results show that the post-forging process of 1 050 ℃ normalizing + isothermal annealing yields a more uniform spheroidal pearlite microstructure. The microstructure obtained by 1 000 ℃ normalizing + isothermal annealing is identical to that of the conventional annealing process， namely carbide-depleted zones exist in the microstructure， and chain-like carbides precipitate along twin boundaries， and these features are inherited by the tempered microstructure. The non-uniform annealed microstructure has a significant effect on the impact toughness of the steel. The impact toughness of the steel treated by 1 050 ℃ normalizing + isothermal annealing + quenching and tempering is 77%–80% higher than that of the steel treated by 1 000 ℃ normalizing + isothermal annealing + quenching and tempering process.