Abstract: The invention relates to the technical field of amorphous soft magnetic material, specifically relating to the field of Fe—Co based amorphous soft magnetic alloy and preparation method thereof. The Fe—Co based amorphous soft magnetic alloy provided in the invention has chemical composition of FeaCobSicBdCue, which possesses merits of highly-saturated magnetic induction, outstanding soft magnetic property and great amorphous forming ability at the same time; the embodiment of Fe—Co based amorphous soft magnetic alloy disclosed in the invention has indicated that its saturation magnetic induction is 1.79˜1.86 T, coercivity 1.4˜4.3 A/m, and permeability 8000˜14000; the invention has advantages of easy treatment process, low annealing temperature, which reduces process cost remarkably and economizes energy, thus having great application prospect.