Black is an important body color of Koi (Cyprinus carpio Koi) which is performed through melanin synthesized by melanocyte, and tyrosinase is an important rate-limiting enzyme in melanin synthesis. It's unclear of genetic mechanism of Koi body color. The present work obtained Koi tyrosinase (Tyr) gene sequence and investigated the expression of Tyr gene in different strains and tissues using semi-quantitative PCR, trying to reveal the relationship between the pigment control genes and the body color. The results showed 1779 bp of Tyr gene, including a 1608 bp open reading frame encoding 535 amino acids. Sequence analysis of cDNA and protein and phylogenetic analysis indicated that conservation of Tyr is higher in teleost than between teleost and other vertebrates. Semi-quantitative analysis showed the highest Tyr expression in the eye and black skin, intermediate in brain, red and yellow skin, and lowest in liver and heart. There was no significant difference of Tyr expression between the same tissues of eyes, liver, heart, brain from different Koi carps, but differentiated in the skins with the highest in black skin, followed by red and yellow skin and small amount in white skin. The different expression was related to tissue function. The role of tyrosinase in non-melanoma cells was unclear. It possibly exist multiple forms of tyrosinase, some of which is inhibited, or the xanthophores and erythrophores could be translated into functional melanocytes.