The short-wave-sensitive 1 (sws1) gene was knocked out using CRISPR/Cas9 technology in zebrafish. Under UV illumination, the numbers of melanocytes were calculated and the expression levels of melanocyte formation related genes pomc and asip, retinoic acid synthesis related genes raldh2 and raldh3 were determined in the dorsal and ventral skins of AB wild type and sws1^-/- zebrafish. It showed that:the number of melanocytes in the dorsal skin of sws1^-/- mutant was significantly less than that of wild type after exposing to UV light for 60 and 100 days;qRT-PCR showed that the expression of pomc in the dorsal skin of sws1^-/- mutant zebrafish was significantly lower than that of wild-type after 100-day UV illumination; the expression of raldh2 in the dorsal skin of sws1^-/- mutant zebrafish was significantly lower than wild-type after 100-day UV illumination. This research suggested that UV light could influence the expression of raldh2 and the synthesis of retinoic acid through sws1, and then affected the expression of pomc to regulate melanocyte formation. This result provided a basis for understanding the molecular mechanism of sws1 regulation on melanocyte formation of the fish skin.