Optimizing plant architecture apt for high-density planting is an effective strategy for increasing crop yields. Breeding of ideotype crop is currently hindered by the lack of deployable genes and elite germplasm. In this study, we uncover a prevalent role of accumulation of homozygous favorable alleles of genes regulating four major morphological traits (plant height/ear height, leaf angle, tassel branch number, and flowering time) constituting maize ideotype, through decoding the breeding history of hybrid maize in China. Utilizing map-based cloning and association mapping, we identify and functionally validate eight genes regulating these traits. Guided by genomics and molecular markers, we developed four new maize hybrids that are better apt to high-density planting with increased yields, compared to two elite hybrids dominantly cultivated in China nowadays. This study sheds light on the genomic framework underlying plant architecture regulation in hybrid maize, and exemplifies the effectiveness of genomics-empowered breeding of ideotype crops.