Si/C composite materials have attracted enormous research interest as the most promising candidates for the anodes of next-generation lithium-ion batteries, owing to their high energy density and mechanical buffering property. However, the major disadvantage of materials with ultra-high capacities, such as Si-based materials, is the significant volume change during cycling, which further leads to mechanical and electrochemical degradation. A comprehensive computational model is indispensable in the developing process of the excellent performance of anode material due to the low realizability, inconvenience, and high cost of experiments, which also provides powerful tools for fabrication guidance of novel Si/C composites designs. Hence, this study explores the multiphysics behavior of Si/C anodes material from the atomic level to cell level using DFT modeling and FEA methodology, systematically revealing the coupling mechanism among various physical fields, as well as providing efficient and powerful tools in the design, development, and evaluation of high energy density lithium-ion batteries.