Abstract: The ventri-yellow pigmentation mouse (temporarily named VY^Slac) arose spontaneously in the C57BL/6J inbred mouse strain, found and bred by Shanghai SLAC Laboratory Animal Co., Ltd. VY^Slac presented a special phenotype marked by yellow coat on the ventral surface of neck and trunk that was without melanin deposition but maintained a normal structure. The number of melanocytes in epidermis and melanin in hair follicle of the abdominal skin of the mutant mouse were less than that of their background strain, while there was no significant difference between the dorsal skins of the two strains. This mutant phenotype was inherited as single-gene dominant inheritance, confirmed by genetic experiment, and there was no significant difference between VY^Slac and B₆ for other biological parameters such as weight, anatomic and histological structures of major organs and blood physiology. When the linkage relationship between the genomic DNA samples of F2 48 mice (VY^SlacD₂F₁₂) and mutant phenotype were evaluated, the mutant gene was confirmed on chromosome 2 near D2Mit229. New microsatellite and SNP markers were selected to amplify genomic DNA samples of 196 F₂ mice and the mutant gene was narrowed down to 5.3 Mb region between rs13476833 and rs27310903 on chromosome 2. The preliminary results of our phenotype analysis and gene location provides a solid basis for further identification of this mutant gene.