To develop high-yield and high-quality maize varieties and alleviate the supply-demand pressure arising from the difficulty in balancing high yield and high quality, this study used a near-infrared analyzer (DA7250) to measure the protein, starch, and oil content in 588 elite maize inbred lines (across four environments) and 939 landraces (across two environments).Integrating multi-year and multi-location data, phenotypic variation, differences between the two populations, and correlations among the traits were analyzed. The results indicate that:(1) Landraces exhibit high genetic diversity Shannon-Wiener index H′ > 2.0 for all three quality traits, with oil content displaying the highest phenotypic variation at CV=8.66% and starch content the lowest at CV=2.46%. Protein content is significantly higher in landraces from the Southwest region than in those from the Huanghuai region (P=1.4×10??), whereas starch content is significantly lower (P=0.000164). (2) Elite inbred lines also exhibit rich diversity with H′ values for protein, starch, and oil being 2.075, 2.049, and 1.980 respectively. The coefficient of variation for protein and oil content exceeds 10% in specific environments, and both traits overall show a decreasing trend in content from south to north. (3) Landraces possess significantly higher protein (P=3.77×10??3) and oil content (P=4.8×10?13?) than elite inbred lines, with no significant difference in starch content. (4) Highly significant correlations exist among the traits (P<0.01): starch content is negatively correlated with both protein and oil content, whereas protein and oil content are positively correlated. (5)Four accessions with high-protein and high-starch and three accessions with high-oil and high-starch were identified, providing key resources for analyzing the synergistic improvement mechanism of maize yield and quality; simultaneously, extreme quality materials ranking in the top 10 for protein, starch, and oil content were selected, including widely used core inbred lines such as HZ32, PH4CN, and Su37. In summary, both landraces and elite inbred lines harbor abundant quality trait variation. This study provides a material foundation for developing high-quality maize varieties and offers practical guidance for quality breeding practice.