Fecundity is one of the main characters of sheep. How to increase the fecundity of sheep has been studied by researchers in China and abroad. Fec B gene was found to be related to the fecundity of sheep. In recent years, genetic molecular markers were used in the breeding of high fecundity sheep. It was found that FecB gene indwells in Wadi sheep, Duolang sheep and Cele sheep, little tailed Han sheep and Du Han hybrid sheep of China. Moreover, FecB gene may be the main multiple gene of these sheep. FecB gene can improve the ovulation and lambing, but the number of ovulation increased is effect of the rate of embryos survived. We can make a plan of scientific breeding by choosing excellent matrix and using the stress resistance of local sheep for the breeding of sheep. This article is a review on the mechanism of Fec B gene, the distribution of varieties in different areas. The use of the gene was also discussed.