The invention discloses a concrete corrosion inhibitor and a preparation method thereof. The corrosion inhibitor is a compound with a 1-dihydroxyethyl amino-3-alkylamino-2-propanol structure and is prepared by two-step reaction. The method comprises the following steps of: reacting an epoxy derivative with diethanolamine under the action of a catalyst, reacting a product with organic amine, neutralizing a product, distilling, and performing suction filtering to obtain liquid, namely the corrosion inhibitor. The synthesis process is simple, and the prepared corrosion inhibitor has the advantages of high efficiency, corrosion inhibition, environment friendliness, high dispersibility and the like, and does not have any adverse effect on the performance of concrete.