The ferrite phase strengthened by the highly dense nanometer-sized carbides is named super ferrite. The effects of Ti, Ti-Mo, and Ti-Nb micro-alloy additions on the precipitation strengthening in three experimental high-strength low-alloy steels have been investigated by using transmission electron microscopy and micro-hardness measurement. The objective of this work was to study the carbide precipitation under the conditions of isothermal transformation. It was found that interphase precipitation of nano-sized carbide in Steel Ti-Mo had very strong contribution to the hardness of the steel. The distribution of interphase precipitated carbides is associated with both the sheet spacing and the inter-particle spacing, which have been studied. The result implies that (Ti, Mo)C particles possess an excellent effect on precipitation hardening.