The invention belongs to the design and preparation technology of bulk metallic glass materials, and in particular to a liquid-phase separation biphasic bulk metallic glass material and a preparation method thereof. The liquid-phase separation biphasic bulk metallic glass material comprises a liquid-phase separation alloy Zr-BE formed by alloy elements of Zr and BE, and an added other alloy element i to respectively form Zr-enriched and RE-enriched two metallic glass phases under the condition of quick cooling. Before the glass transition of an alloy melt occurs, liquid-liquid phase separation occurs firstly to generate Zr-enriched and RE-enriched two liquid phases; and the added other alloy element i is selectively distributed in the two liquid phases to respectively evolve to areas near eutectic components of respective alloy systems so as to achieve strong amorphous forming ability. In the following quick cooling process, glass transition occurs on the two liquid phases, and a biphasic bulk metallic glass bar is prepared through copper mold casting; the diameter of prepared Zr-based biphasic bulk metallic glass is within 1-3 mm; and the diameter of prepared RE-based biphasic bulk metallic glass is within 1-2 mm.