There are provided metallic glass matrix composites with controllable work-hardening capacity. In more detail, there are provided metallic glass matrix composite with controllable work-hardening capacity capable of having significantly excellent toughness due to a metastable second phase precipitated in-situ in a metallic glass matrix by polymorphic phase transformation during a solidification process without a separate synthetic process, and capable of controlling work-hardening capacity by measuring physical properties of a second phase and adjusting a volume fraction (Vf) of the second phase due to constant correlation between the physical properties (absorbed energy Eta, a phase transformation temperature TMs, or a hardness H2nd) of a metastable B2 second phase precipated in the metallic glass matrix and the absorbed energy (Epa,V) by work-hardening per unit volume fraction of the second phase in the metallic glass matrix.