A nonlinear model was developed to describe the relationship between tensile ductility and constituents in micron scale as well as dispersoids in sub-micron scale in aluminum alloy based on the formation of various-sized micro-cracks during deformation.The model prediction agrees well with the experimental data.Effects of the volume fraction and size of the various-sized constituents and dispersoids on tensile ductility of aluminum alloy can be quantitatively analyzed by means of the model.Meanwhile,measures of improving tensile ductility of aluminum alloy were taken based on the simulated results.