Disclosed are a novel self-assembled amino acid supramolecular polymer, a preparation method therefor, and an application thereof. The self-assembled supramolecular polymer is N-lauroyl-L-alanyl-L-alanine or a salt thereof, and the salt thereof comprises sodium N-lauroyl-L-alanyl-L-alaninate and potassium N-lauroyl-L-alanyl-L-alaninate. The disclosed polymer is more effective at inhibiting bacteria and removing pesticides, and can be widely applied to the daily chemical, agricultural, and pharmaceutical industries. Further disclosed are three methods for preparing the compound. The methods produce products in high yields and are suitable for industrial production.