Zebrafish (Danio rerio) is a common model organism, red zebrafish is one of the small ornamental fishes. The body color of fish is mainly determined by the tape and distribution of pigments on the skin or scales. Melanocytes inducing transcription factor (MITF) mainly regulate the development and differentiation of animal melanocytes. We observed the composition and distribution of pigment cells in the dorsal, anal, pelvic, ectoral of adult red zebrafish, and tracked the early body color development process of the red zebrafish. The knockouting system of mitfa gene was constructed by CRISPR/Cas9 gene knockout technology, which is to study how mitfa gene plays a role in early color development of red zebrafish. The results showed that: 1) Red pigment cells, xanthophores and a small amount of iridophores cells are distributed on the red zebrafish fin, but there are a large number of melanocytes in the dorsal fin; 2) During the early body color development of the red zebrafish, melanocytes appear first and then xanthophores appeared. One month later, the melanocytes of the red zebrafish faded, and the surface of the fish became light red. Then the color of the body surface gradually deepened during the discoloration, and finally the body color of the adult fish with red and silver-white stripes alternately distributed; 3) Using CRISPR/Cas9 technology to knock out the mitfa gene, it was found that the absence of mitfa resulted in significantly fewer melanocytes in the early red zebrafish. The above research results will provide important theoretical support for the selection and breeding of ornamental fish and the establishment of effective ways to artificially improve the body color of fish.