The invention provides an iron-based amorphous alloy as shown in a formula (I), wherein each of a, b and c represents the atom percentage of a corresponding component, a is larger than or equal to 80.0 and is smaller than or equal to 82.0, b is larger than or equal to 11.0 and is smaller than or equal to 13.0, c is larger than 6.5 and is smaller than or equal to 8.0, and the sum of a, b and c is 100. The invention provides an iron-based amorphous alloy strip, and the saturation induction density of the alloy material is not lower than 1.60T. The application also provides a preparation method of the iron-based amorphous alloy, further, heat treatment can be carried out in a wide heat treatment range, the iron-based amorphous alloy strip with good soft magnetic property can be obtained, and the alloy material can be used as an iron core material or a magnetic core material for manufacturing power transformers, power generators and engines; and FeaBbSic is as shown in (I).