The invention provides a method for crystallizing Fe-based amorphous alloys, comprising the following steps: (1) mixing Fe-based amorphous alloy powder and crushed diamond powder in a certain proportion, then adding a composite binder and mixing uniformly to obtain a mixture; (2) pressing the mixture into a regular shaped preform; (3) placing the preform in a drying oven for drying to obtain a dehydrated preform; (4) placing the dehydrated preform into a tube furnace for the first stage of high-temperature treatment, and cooling to obtain a degreased mixture skeleton; (5) placing the degreased mixture skeleton and aluminum into a tube furnace for the second stage of high-temperature treatment, and cooling to obtain a controlled crystal morphology after the crystallization process of the Fe-based amorphous alloy. The preparation method provided by the invention allows the Fe-based amorphous alloy to undergo self-heating during the crystallization process, using crushed diamond as a seed, and with the passage of time, the Fe-based amorphous alloy and diamond grow together into a regularly shaped crystal morphology structure.