The invention discloses a preparation method and application of a scallop skirt whitening peptide. The preparation method of the whitening peptide comprises the following steps: (1) scallop skirt pretreatment: taking scallop skirts, cutting into pieces, adding a set scallop skirt mass multiple of water for homogenization to obtain scallop skirt homogenate; (2) enzymatic hydrolysis: sequentially adding pepsin and trypsin into the scallop skirt homogenate in the step (1) for enzymatic hydrolysis to obtain an enzymatic hydrolysate; (3) adjusting the pH of the enzymatic hydrolysate to 6.8-7.2, centrifuging, taking a supernatant for concentration, adding a set proportion of absolute ethanol, stirring, precipitating the ethanol, centrifuging and taking a supernatant, namely a scallop skirt polypeptide crude extract; purifying to obtain the scallop skirt whitening peptide. The scallop skirt whitening peptide capable of significantly inhibiting the tyrosinase activity can be obtained only through simple double enzymatic hydrolysis and an ethanol precipitation process, has application potential of effective ingredients in whitening cosmetics and simultaneously has the advantages of high activity, good biocompatibility, safety and no side effect.