The relative glass forming ability (GFA) of bulk amorphous Zr 6 0 Cu 2 0 Ni 8 Al 7 Hf 3 Ti 2 (A 1 ) and Zr 5 2 . 5 Cu 1 7 . 9 Ni 1 4 . 6 Al 1 0 Ti 5 (Vit105) alloys has been investigated by comparing the maximum thickness of amorphous region of wedge-shaped samples, as well as the evaluated critical cooling rates using differential thermal analysis (DTA). The results show that the maximum thickness of amorphous region of wedge-shaped samples are d m =2mm for A 1 , d m =3.5mm for Vit105, and the evaluated critical cooling rates are R c =33.5 and 4.5K/s for A 1 and Vit105, respectively. It is suggested that the glass forming ability of A 1 is smaller than that of well known Vit105 alloy, though A 1 has the significant supercooled liquid region of over 140K. Therefore, it is concluded that a large supercooled liquid region ΔT x does not necessarily mean good glass forming ability of an amorphous alloy.