The mechanical properties of nano-scale Cu/FeS composite were simulated by molecular dynamics (MD) simulation in this paper. Through the analysis on the stress-strain curves, the results of MD simulation were in good agreement with mechanisms of macroscopic deformation. When the size of particles was smaller than a certain value, the relationship between yield strength and size, which was different from the large size crystals abided by the contrary Hall-Petch relationship. Based on the discussion of nano-scale Cu/FeS composite, some interesting conclusions were obtained. For example, the “S” type curves were discovered in stress-strain curves and the anisotropy of FeS was very evident when the exposures of reinforcing phase (FeS) were different and so on. The basic theories and calculations of the composite that contains nano-scale particles were discussed. At the same time, a new modeling building method of composites, which was close to actual experiences, were considered in this paper. The mechanical properties of nano-scale Cu / FeS composite were simulated by molecular dynamics (MD) simulation in molecular dynamics (MD) simulation in this paper. Through the analysis on the stress-strain curves, the results of MD simulation were in good agreement with mechanisms of macroscopic deformation. the size of particles was smaller than a certain value, the relationship between yield strength and size, which was different from the large size crystals abided by the contrary Hall-Petch relationship. Based on the discussion of nano-scale Cu / FeS composite, some interesting conclusions were obtained. For example, the “S ” type curves were discovered in stress-strain curves and the anisotropy of FeS was very evident when the exposures of reinforcing phase (FeS) were different and so on. The basic theories and calculations of the composite that contains nano-scale particles were discussed. At the same time, a new modeling building method of composites, which was close to actual experiences, were considered in this paper.