The dataset presents a FAIR (Findable, Accessible, Interoperable, and Reusable), comprehensive, long-term dataset documenting maize phenology dynamics across China's Huang-Huai-Hai Region (HHHP), a critical area for national grain production. Spanning the period 1981–2024, the dataset integrates observations from 101 agrometeorological stations across eight provinces and municipalities, capturing ten key phenological stages—from sowing to maturity—and deriving four critical growth lengths. A multi-tiered quality control protocol, including automated consistency checks, climate data cross-referencing, and expert arbitration, was applied to ensure data integrity. Analytical outputs include kernel density estimation for characterizing probability distributions and univariate linear regression for quantifying decadal trends. The dataset comprises 1,616 diagnostic plots in JPEG format and two core data tables in XLSX format, with a total uncompressed volume of 1.50 GB.</p> <p>The dataset is publicly available via the Science Data Bank under the accession code <a href="https://doi.org/10.57760/sciencedb.32076" target="_blank" rel="noopener">https://doi.org/10.57760/sciencedb.32076</a> and supports diverse applications in climate impact assessment, crop model improvement, and adaptation strategy development.