The SPS sintering process is used in this study to create 50 wt % micro-sized spherical Fe-based metallic glass powders reinforced magnesium matrix composites (FMGP). The release of trace amounts of Cr in Fe-based metallic glass particles due to a positive mixing enthalpy with Mg not only improves the mechanical suitability of the interface between the metallic glass and the matrix but also contributes to the solution to the increasing problem of fracture toughness of the composite. Following the inclusion of metallic glass particles (50 wt %), the tensile strength (23%), yield strength (50%), and plasticity (more than 8%) were significantly increased. The Cr diffused to the interface and dissolved into the MgO in the form of replacement, forming the oxidation transition layer with the MgO and α-Mg at the interface and distributed among a discontinuous form, according to the analysis of the high-resolution transmission diagram of the composites and the calibration of the diffraction spots of the magnesium matrix at the interface. This enhances mechanical interface matching and transforms the composite's fracture process from inter-crystalline to quasi-destructive, increasing the material's fracture toughness. Once established, the model's first-principles computation and analysis are consistent with the test results.