The simple shear molecular dynamics (MD) simulations areperformed on single-crystal copper blocks to analyze the size and strainrate effects on face-centered cubic (FCC) metals. It is found that the yieldstress decreases with the specimen size and increases with the strain rate.Based on the theory of dislocation nucleation, a modified power law isestablished to predict the scaling behavior of FCC metals, and it agreeswell with the numerical and experimental data ranging all spatial domainfrom nano-scale to macro-scale. In the atomistic simulation at differentapplied strain rates, a critical strain rate exists for the single-crystalcopper. Below it the yield stress is nearly insensitive to the strain rate,while above it the yield stress increases rapidly with increasing strainrate. Based on the results of the MD simulation, a strain rate model isintroduced for the plastic yield stress of FCC metals at nano-scale.