The invention relates to an iron-based bulk metallic glass alloy with a large supercooled liquid phase region and belongs to the technical field of novel materials. The iron-based bulk metallic glass alloy with the large supercooled liquid phase region is characterized by consisting of iron, nickel, cobalt, molybdenum, chromium, tungsten, phosphorus, carbon, boron and silicon and having a composition expression of FexNiyCozMoaCrbWcPdCeBfSig, wherein x, y, z, a, b, c, d, e, f and g respectively represent atom percent content of each corresponding component; x is 50 to 70 percent; y is 0 to 20 percent; z is 0 to 15 percent; a is 2 to 6 percent; b is 0 to 4 percent; c is 0 to 3 percent; d is 8 to 15 percent; e is 10 to 12 percent; f is 2 to 6 percent; g is 0 to 2 percent; x+y+z is 50 to 75 percent; a+b+c is 4 to 10 percent; and x+y+z+a+b+c+d+e+f+g is equal to 100 percent. The alloy has the typical composition expression of Fe55Co10Ni5Mo5P10C10B5. The iron-based bulk metallic glass alloy has the effects and the benefits that the alloy simultaneously has the advantages of low glass transition temperature, large supercooled liquid phase interval, high glass-forming ability, low coercive force, excellent mechanical performance, low viscosity coefficient in a cold liquid phase interval and the like, can implement micron-grade and nano-grade superplasticity processing, and is a novel iron-based soft magnetic metallic glass alloy for superplasticity processing, with low production cost.