Abstract: K12 self-bred line was bred by the self-bred line with high- combining ability Huangzaosi and material with subtropical germplasm in southwest of China. The authors had integrated the recurrent selection in corn strain population with the pedigree method. K12 self-bred line is extensively in all over China because it has high combining ability, high resistance to adversities, wide adaptabilities and the superior comprehensive agronomic properties. Since the 90th of this century, over 10 hybrid maize varieties have been combined with K12 self-bred line with 4.67 million hectares planting area. K12 self-bred line played significant roles in the maize breeding and production in China.