During recent years, AI in swine production has been implemented extensively, thus, the selection of AI boars has become increasingly urgent and critical to the pig industry. Yet, boar reproduction is a complex physiological process with a low heritability, so it is hard to estimate breeding value of boars for male reproductive traits. Currently, molecular breeding provides a new tool to increase rate of response to boar selection such as some candidate genes, which have been suggested for marker-assisted selection (Chen et al. 2004; Nonneman et al. 2005; Lin et al. 2006). Yet, candidate-gene approaches are too often non-reproducible and effects of candidate markers are always population specific (George 2007). Efforts have been directed toward detecting quantitative trait loci (QTL)significantly affecting the male reproductive traits using intercross populations between Chinese Meishan and Western commercial breeds (Rohrer et al. 2001; Bidanel and Rothschild 2002;Sato et al. 2003), with an ultimate goal of identifying the quantitative trait nucleotides underlying these complex traits.