Abstract: Metallic glass and metallic glass matrix composites have good application prospects because of their excellent mechanical properties, and now more and more researches have been conducting on them. The deformation behavior, toughening mechanism and constitutive relationship of metallic glass matrix composites are summarized and reviewed in this paper, based on the existing research results in literature by other groups and the latest work done by the authors. Firstly, the research progress in the deformation behavior, failure mechanism and constitutive relation of metallic glass in recent decades is briefly reviewed. Then, the state-of-the-arts in the deformation behavior and failure mechanism of metallic glass matrix composites are introduced from the aspects of experiments and numerical simulation, and the plastic deformation, toughening mechanism and their correspondent influencing factors of metallic glass matrix composites are summarized. Furthermore, the existing studies on the constitutive equations of metallic glass matrix composites are reviewed, with emphasis on the application of homogenization method in this field. In addition, a two-stepped homogenization method proposed by the authors is introduced in more details as a representative approach, and then the constitutive model established on the two-stepped homogenization method and with a help of a failure criterion obtained by introducing a concentration of nano-voids as an internal variable is addressed. The deformation and failure behavior of metallic glass matrix composites are predicted reasonably by the proposed constitutive model. Finally, the research progress of this field is briefly summarized, and some future topics are suggested.