Abstract: In oder to evaluate the ASIP loci in color Rex rabbit， gene polymorphism at ASIP loci and the structure of protein were studied， the evolutionary tree of leporidae was also constructed. The resluts showed that three alleles were found at this loci in the color Rex rabbit， A: light\|bellied agouti（wild type）， including brown and chinchilla color; at: tan\|agouti， including tan color; a: non\|agouti， including black， yellow and blue color. Phylogenetic and homologies analysis of the genes at agouti loci from color Rex rabbits and other species of leporidae showed that color Rex rabbits had the highest genetic relationship with Lepus europaeus. Wild type ASIP gene and tan\|agouti gene both encoded a sequence of 133 amino acids with a 24\|amino signal peptide and a cysteine\|rich hydrophobic region at C\|terminal， so this protein had important biological activity. But the differences of these two protein sequences， especially in the conserved regions， caused the change of eumelanin and phaeomelanin， which made the Rex rabbits exhibit different coat color. Non\|agouti gene encoded a sequence of 21 amino acids， it was unstable and could not produce ASIP， so the coat color was black/dark in Rex rabbit.

Key words: color Rex rabbit, agouti, ASIP, gene polymorphism