CuZr phase is precipitated easily in the process of fabricating Zr 50.5 Cu 34.5 Ni 4 Al 11 BMG. The critical diameter of amorphous rod is improved from 8mm of Zr 50.5 Cu 34.5 Ni 4 Al 11 to at least 20mm of Zr 53.5 Cu 26.5 Ni 5 Al 12 Ag 3 by restraining the precipitation of CuZr phase. The great improvement of GFA is attributed to the declination of Cu content and the weakening of the drastic interaction between Cu and Zr atoms by Ag addition since Ag has similarly physical and chemical properties with Cu. Therefore, suppressing the precipitation of crystalline phase should be an effective method to enhance GFA.