Abstract: Investigate the aging dynamics of HSLA100 steel by hardness measurement and TEM observation. The results indicate that aging dynamics of HSLA100 can be discribed by Avrami equation. The apparent activation energy for the aging process is 140 kJ/mol, which has been reduced by the presence of excess vacances and high dislocation density. Also it has been proved that the coarsening process of ε-Cu obeys the Ostwald mechanism.