Abstract: The goal of this study is to breed a swine synthetic line with the characteristics of high efficiency, high productivity and large body weight for marketing.Guided by the theory of quantitative genetics and molecular genetics, we adopted the method of combining conventional breeding with marker assisted selection to breed a swine synthetic line named WS501, which consisted of five specialized lines with high productivity and large body weight for marketing, from domestic and abroad germplasm resources. High reproductive performance were observed in W352 sows, indicating that the average litter size of first-born and multiparous sows were 12.86 and 13.10 respectively, the number born alive were 11.71 and 12.00 respectively, and the litter birth weight were 14.59 and 15.96 kg respectively. Testing results of WS501 commercial pig showed that the adjusted back fat thickness at 100 kg was 11.0 mm, the time to reach 100 kg body weight was 147 d, the average daily gain from 30 to 100 kg was 1 004 g, feed conversion ratio was 2.12, carcass lean percentage at 100 kg body weight was 65.8%, and the variation coefficient of these traits were below 10%. W501 commercial pig has the characteristics of muscularity, fast growth, high feed conversion ratio, high lean percentage and good meat quality. It is suitable for marketing at large body weight, and good comprehensive economic benefit can be obtained. It can be widely used in large-scale pig production in China.