An oligopeptide with lipid-lowering activity, a preparation method and an application thereof are provided, belonging to the field of biotechnology. The amino acid sequence of the oligopeptide with lipid-lowering activity is shown in SEQ ID NO: 1. The preparation method includes the following steps: (1) hydrolyzing a loach protein with proteases to obtain an enzymatic hydrolysis product; (2) separating the enzymatic hydrolysis product using an ultrafiltration membrane, and taking a component with a molecular weight less than 3 kilodalton (kDa); and (3) filtering and separating the component with the molecular weight less than 3 kDa by Sephadex G-15 to obtain the oligopeptide. The oligopeptide is derived from the loach protein and has the characteristics of high safety, high efficiency, and wide sources.