To comprehensively describe the size and strain rate dependent yield strength of monocrystalline ductile materials, a theoretical model was established based on the dislocation nucleation mechanism. Taking Ni₃Al as an example, the model firstly fits results of molecular dynamics simulations to extract material dependent parameters. Then, a theoretical surface of yield strength is constructed, which is finally verified by available experimental data. The model is further checked by available third part molecular dynamics and experimental data of monocrystalline copper and gold. It is shown that this model can successfully leap over the huge spatial and temporal scale gaps between molecular dynamics and experimental conditions to get the reliable mechanical properties of monocrystalline Ni₃Al, copper and gold.