The study compared the grain quality of Chinese and U.S. maize hybrids from the 1960s to 2000s. Chinese hybrids had lower starch but higher oil and protein levels than U.S. hybrids. Chinese hybrids showed a gradual increase in starch content over the decades, while U.S. hybrids also increased but to a lesser extent. Chinese hybrids had more significant changes in grain quality with planting density and environment compared to U.S. hybrids. The introduction of U.S. maize germplasm in China led to decreases in oil, protein, and lysine levels in Chinese hybrids, but by the 1990s, Chinese hybrids had similar grain quality to U.S. hybrids. To improve grain quality in Chinese maize hybrids, selecting high-quality parental inbred lines alongside yield improvement is necessary.