Zr-based metallic-glass matrix composites, which are reinforced by continuous tungsten fibers, were prepared by melt infiltration casting. The interface structure was analyzed by using X-Ray diffraction, SEM and EPMA. The results illustrate that for the Zr55Al10Ni5Cu30 matrix composite, in addition to the interface diffusion, an interface eutectoid reaction between W fiber and Zr in the liquid state takes place and forms W5Zr3 phase at the interface during casting, the interface is included in Class III system; but for (Zr55Al10Ni5Cu30)(0.98)Nb-2 and Zr57Al10Ni12.6Cu15.4Nb5 matrix composite, the addition of Nb restrains the interface eutectoid reaction effectively, which may be attributed to reducing diffusion coefficient of Zr through the interface, and there is only a thinner diffusion layer at the interfaces, the type of interface is changed to the Class II system.