Electrochemical anodization is an effective and low-cost technique to fabricate nanostructured metal oxides, however, reports on synthesizing Fe3O4 on iron substrate are still few up to date. Herein we report a facile and scalable fabrication of Fe3O4 film by a rationally designed strategy of electrochemical anodization and low-temperature crystallization processes. The self-supported Fe3O4 film composed of polyhedral nanocrystals is successfully fabricated on iron substrate. It is noted that some common conditions for synthesizing crystalline Fe3O4 such as ferric salts and annealing are avoided. The Fe3O4 film is derived from the iron substrate and proved to be considerably robust, which could be employed as catalyst and electrode. The strategy for fabricating Fe3O4 nanocrystals on iron substrate in this study is expected to inspire the exploration of low-temperature crystallization for other metal oxides. (C) 2019 The Electrochemical Society.