The brief development history and dominant factors of forming ability of bulk amorphous alloys were surveyed. The forming mechanisms of bulk amorphous alloys were investigated from the viewpoints of thermodynamics, kinetics and structure. The criteria for bulk amorphous alloys design were introduced. It was pointed out that,molten metal having high density random close-packed topology structure, restraining the homogeneous nucleation and nuclei growth of the supercooled melt as possible, increasing the cooling rate and reducing or eliminating heterogeneous nucleation,would be helpful to form bulk amorphous alloy.