Liaozong maize population was created from American germplasm as basic materials. Three circles of the improvement on Liaozong maize population were made by the methods of S1 phenotypic selection, S1 high-density selection, and combining ability selection. Breeding potential on the 8 populations had been evaluated systematically. The results showed that the S1 high-density selection method has gained a better result, which is characterized by its simple, convenient and functional method on pratical operation. Synthetic groups of Liaozong C3-3 were better on rows of ears, higher yield level(GCA) and great potential of breeding material. The method of S1 density selection was used for further two cycles improvements with new germplasm introduced into Liaozong C3-3. Six good hybrids from different cycle populations were approved by national or provincial maize cultivar registration board, which had been released with an acreage of 1.225 million hectares.