To further improve the mechanical properties of carbon nanotubes (CNTs) modified aluminum alloy (ZL105), the first principle was used to build the atomic structure of the alloy system and the alloy system was simulated by the VASP. After that, the heat treatment process of the cast aluminium alloy material with CNTs to enhance the alloy performance by the orthogonal experiment. The results of the research show that: (1) The energy status of the alloy system could be changed by adding the C atoms, but it did not affect the formation and structural stability of the alloy system, and the strong bond compounds formed by C atoms with other elements inside the solid solution structure can significantly affect the material properties. (2) The time of solid solution has the greatest influence on the performance of material that was modified by CNTs. The solution temperature and aging temperature were lower strength affection, and the aging time is the lowest affection. This paper provides a new research method of combining the atomic simulation with the casting experiment, which can provide the theoretical calculations to reduce the experiment times for the casting materials’ performance improvement.