Abstract: To finely map and identify the mutant gene of snthr^-1Bao mouse whose mutation gene showing single gene recessive heredity was mapped on the terminal side of chromosome 9，F₂ mice bred through (C57BL/6J ×snthr^-1Bao )F₁ mice intercrossing and the polymorphisms of 2 microsetallites, 35 SSRs presumed by computer and 3 SNPs chosen and tested were for fine mapping. RT-PCR amplifying cDNA combined with genomic sequence to identify mutation after affirming candidate gene. Based on genomic markers D9Mit151, a new SSR，two SNPs (rs8 254 361 and rs30 195 705) and 1 100 F₂ scant hair mice selected from over 4 400 F₂ mice, the mutant gene was narrowed down to a 1.367 Mb region between 117.762 kb and 119.129 kb from the centromere on the chromosome 9 and Plcd1was the primary candidate gene. Genomic sequence revealed there was a 14 883 bp deletion and such deletion destructed the Plcd1 and Vill. The 14 883 bp genomic deletion covering subtotal Plcd1and Vill, more likely the Plcd1, is responsible for the abnormal phenotype of snthr^-1Bao mouse.