Abstract: The W^-3Bao mouse, which was obtained in previous ENU mutagenesis project, is a new mutant caused by the nonsense mutation of Kit gene. Mating and gross observing combining with PCR and sequencing were used for determining the genotypes of the W^-3Bao mice. Embryonic development, hematological detection and histopathologic section methods were used for their phenotype analysis. The results showed that the W^-3Bao/+ mouse was white belly, white limb terminals and white tail tip. However, there was no difference of the external appearance among the W^-3Bao/+, W^-3Bao/3Bao and wild type mice for the embryo of 12.5 days. The W^-3Bao/3Bao embryos looked pale since pregnant 14.5 days and dwarf since pregnant 16.5 days. The extremely low level of haematochrome and big red blood cells of W^-3Bao/3Bao 18.5-day-embryos were found in the inspections of blood routine items and blood smear, which resulted in death of W^-3Bao/3Bao homozygous mouse around being born, and no live postnatal W^-3Bao/3Bao mouse was found in this study. No spermatogonium at different developmental stages was found in some contorted seminiferous tubules in adult W^-3Bao/+ mouse. At the age of 18.5-day embryo, the spermatogonium of W^-3Bao/3Bao mice only lied in interstitial tissue and no one lied in contorted seminiferous tubules, while the spermatogonium of W^-3Bao/+ or W^+/+ mice lied in interstitial tissue and in contorted seminiferous tubules in the same time. At the age of 18.5-day embryo, cells arranged irregularly and primordial follicles were not seen in the W^-3Bao/3Bao ovaries, while primordial follicles appeared clearly in the ovaries of W^-3Bao/+ or W^+/+ mice. We concluded that because of the nonsense mutation of Kit gene, the W^-3Bao/+ mice show white spot and abnormal development of some contorted seminiferous tubules. The W^-3Bao/3Bao mice die around birth resulting from severe macrocytic anemia and show abnormal genital glands of both genders.