The invention discloses a preparation method of iron proteinsuccinylate. The preparation method comprises the steps of 1, dissolution and acylation; 2, membrane filtration; 3, membrane separation; 4, iron carrying; 5, membrane filtration; 6, membrane separation; and 7, refined filtration, precipitation and drying. According to the preparation method, by improving a key impurity separation technology step in the preparation technology, compared with the prior art, repeated and complicated preparation technology steps can be effectively reduced, the risk of microbial contamination in the preparation process is greatly lowered, and the by-product succinic acid generated in the acylation process and ferric ions not involved in a reaction in the iron carrying process are effectively removed; moreover, the production process is continual, technology time is short, and production efficiency can be greatly improved.