Nanocomposite tool materials are developing very fast in engineering field for their highlighted advantage in mechanical properties and stability under high temperature. However, there are lots of puzzles to be discussed in the materials design theory and the fabrication processing due to the difference between the traditional materials and the nanocomposite. Therefore, in this paper, a new nanocomposite tool materials design method has been proposed based on the interface strengthening theory. The sintering temperature and the soaking time could be optimized based on the interface strengthening theory and the relative density of the tool materials. Meanwhile, a series of experiments were carried out to fabricate the nanocomposite tool materials under the guider of the interface strengthening theory. Results showed that experimental data agreed well with the calculation and the model was proved to be correct.