The tempering stability of three Fe–Cr–Mo–W–V hot forging die steels(DM, H21, and H13) was investigated through hardness measurements and transmission electron microscopy(TEM) observations. Both dilatometer tests and TEM observations revealed that DM steel has a higher tempering stability than H21 and H13 steels because of its substantial amount of M_2C(M represents metallic element) carbide precipitations. The activation energies of the M_2C carbide precipitation processes in DM, H21, and H13 steels are 236.4, 212.0, and 228.9 kJ/mol, respectively. Furthermore, the results indicated that vanadium atoms both increase the activation energy and affect the evolution of M_2C carbides, resulting in gradual dissolution rather than over-aging during tempering. Both tempering stability of three Fe-Cr-Mo-W-V hot forging die steels (DM, H21, and H13) was investigated by hardness measurements and transmission electron microscopy (TEM) observations. Both dilatometer tests and TEM observations revealed that DM steel has a higher tempering stability than H21 and H13 steels because of their substantial amount of M_2C (M representative metallic element) carbide precipitations. The activation energies of the M_2C carbide precipitation processes in DM, H21, and H13 steels are 236.4, 212.0, and 228.9 kJ / mol, respectively. The results indicated that vanadium atoms both increase the activation energy and affect the evolution of M_2C carbides, resulting in gradual dissolution rather than over-aging during tempering.