Small Tail Han Sheep has significant characteristics of high prolificacy and non-seasonal ovulatory activity and is an excellent local sheep breed in P. R. China. Recently a novel member of the transforming growth factor β (TGFβ) superfamily termed bone morphogenetic protein 15 (BMP15) was shown to be specifically expressed in oocytes and to be essential for female fertility. Therefore, BMP15 is a candidate gene for reproductive performance of Small Tail Han Sheep. The whole genomic nucleotide sequence of BMP15 gene in Small Tail Han Sheep was searched for polymorphisms by PCR-SSCP and direct sequencing, and only one polymorphism was found. The polymorphism was a result of a 3 base pair deletion, which eliminated a single Leu codon (CTT). The allelic frequencies for A (without deletion) and B (with a codon deletion) are 0.73 and 0.27 respectively. The effects of BMP15 genotype on litter size were evaluated using the least squares model. This indicated that there was a significant association between litter size of Small Tail Han Sheep and a deletion in BMP15 gene (p=0.02<0.05). Small Tail Han Sheep ewes with AA and AB genotype produce on average 0.5 and 0.3 more lambs per litter than those ewes with BB genotype.