The nucleus herd was composed of 78 sows and 19 boars of Landrace imported from Hybrid Company of France in 2001, and 210 sows and 8 boars of Landrace from Pig Breeding Center of Beijing in 2002. The open systematic breeding and the Best Linear Unbiased Prediction (BLUP) method were used in the breeding system. The specialized line W52 was obtained after 14 years of breeding.The line W52 possessed the characters of fast growth, high and long body and high reproduction performance. This line was a suitable sire dam line in the WS501 Synthetic Line.