The invention discloses iron-based nanocrystalline soft-
magnetic alloy with excellent high-frequency performance and a preparation method thereof. The expression of the 
alloy is FeaSibPcCuxMy, wherein a, b, c, x and y respectively represent the atomic percent content of corresponding compositions and satisfy the following conditions: 70<=a<=85, 5<=b<=15, 5<=c<=18, 0.0001<=x<=3, 0<=y<=5, a+b+c+x+y=100%, and M is one or more of Zr, Ti, Ta, Hf, Nb, V, W, Mo, Mn, Cr, Re, Zn, In, As, Sb, Bi, Ca, 
platinum group elements, 
rare earth elements, N, Sn, Ge, Ga and Al. The 
alloy is a nanocrystalline soft-
magnetic alloy band prepared by employing a single-roller quick-cooling method under the conditions of high vacuum and 
argon protection. The 
alloy does not contain B elements, is good in soft magnetic property, high in 
thermal stability, low in high-frequency loss and low in 
magnetostriction coefficient.