Abstract: The effects of Co addition on the glass forming ability and mechanical properties of Cu₄₆Zr₄₆Al₈ bulk metallic glass were studied.(Cu_100-xCo_x)₄₆Zr₄₆Al₈（x =0,10,30,50,70,90 at%） bulk amorphous alloy with diameter of 3 mm was produced by copper mold suction casting. The properties of the alloy were tested by XRD and DSC. The compressive properties of the alloy at room temperature were tested. The micro-fracture morphology of the alloy was analyzed by SEM.The results show that the glass-forming ability of the alloy improves by adding appropriate amount of Co element. When the addition amount of Co is 10%, the width of undercooled liquid zone ΔT reaches 62 K, and the amorphous forming ability of the alloy is strongest. When the amount of Co is 70%, the mechanical properties of the prepared amorphous alloy are best,the fracture strength is 2158.25 MPa, and the plastic deformation reaches 1.3%.