Abstract: In recent ten years, with the rapid development of experimental technology, the crystal plastic behavior in sub-micron scale has been well investigated. Numbers of atypical experimental data and theoretical results are revealed. However, they could not be explained by the classical plastic theory in a macro-scale and strain gradient plastic theory in a micro-scale. There are many scientific issues to be resolved. To further investigate the physical nature behind these phenomena, the researchers are trying to find the new theoretic model and numerical method to reveal the characteristics of plastic flow. The defect energy theory and discrete dislocation dynamics method have been proposed in order to describe the evolution of dislocation nucleation, multiplication, starvation and annihilation, and so on. In this paper, the research advances are general reviewed on the relevant experiment methods and data, the theoretical models and numerical methods of crystal atypical plasticity dominated by discrete dislocation mechanism in the sub-micron scale.