The calculation and application of alloy design for DM6S and DM8B high carbon alloy steels with ultra-fine caebides were introduced in this paper. On the basis of carbides transformation orderliness in Cr-W-Mo-V high carbon alloy steel at different temperature, the structure and composition of the phases and its transformation orderliness in the steels at different temperature were estimated by phase-equilibrium thermodynamic calculation for Fe-Cr-W-Mo-V-Si-Mn-Ni-C system. The rational heat treatment technics were concluded on the basis of the matrix composition at different austenitizing temperature, and the hardness of quenching and secondary hardening was doped out. The yield strength and the toughness can be forecasted on the basis of average cohesive-energy of martensit matrix by the calculation at electronic and atomic scale. The practice of two new steels DM6S and DM8B shows that the prospective objective can be obtained by theoretic design adding a small quantity of technical tests.