The effects of Ag (8 at.%), Be (7 at.%), and Gd (2 at.%) addition on structure and thermal stability, as well as bulk glass forming ability, in (Zr52.2Cu39.1Al8.7)(100-x) M (x) (M = Ag, Be, Gd) alloys are investigated by means of X-ray diffraction and differential scanning calorimetry. The alloy containing Ag and Be have a critical diameter of more than 10 mm, with larger supercooled liquid region and atomic packing efficiency than Zr52.2Cu39.1Al8.7 alloy, while the (Zr52.2Cu39.1Al8.7)(98)Gd-2 alloy only has a critical diameter of up to 5 mm and shows smaller supercooled liquid region and atomic packing density. CuZr is the main competing crystal phase with amorphous phase in the present Zr-Cu-based alloys. Ag and Be atoms in Zr52.2Cu39.1Al8.7 alloy decrease the long range diffusion of Cu atoms and hinder the crystallization process under rapid solidification conditions. As a result, the glass forming ability of (Zr52.2Cu39.1Al8.7)(92)Ag-8 and (Zr52.2Cu39.1Al8.7)(93)Be-7 alloys are effectively enhanced.