The Haidai region, renowned for its Neolithic cultural fluorescence (Dawenkou-Longshan traditions), underwent sociopolitical reorganization during the Yueshi period (ca. 1900-1500 BCE). Late Shang (1300-1046 BCE) expansion into Northern Shandong, driven by the Shang polity's control over Laizhou Bay salt resources, catalyzed regional revitalization, yet the agricultural foundations of this transformation remain poorly defined. Through AMS 14C dating, systematic analysis of carbonized plant remains from the Chengxixincun site, and synthesis of regional archaeobotanical datasets, we reconstruct Late Shang agricultural practices in Northern Shandong. Results of the site reveal a foxtail millet (Setaria italica)-dominated dryland system (93.24 % by count; 92.78 % ubiquity), supplemented by broomcorn millet (Panicum miliaceum, 6.12 %), with wheat (Triticum aestivum), soybean (Glycine max), and rice (Oryza sativa) as marginal crops. Weed and fruit remains attest to complementary wild resource exploitation. Comparative analysis demonstrates that Northern Shandong transitioned from Longshan-era rice-millet systems to intensified millet agriculture during Yueshi-period aridification (impact of the 4.2 ka BP event), later amplifying foxtail millet's dominance under Late Shang climatic amelioration and Central Plains agrotechnical diffusion. Crucially, rice cultivation-though never recovering Longshanera prominence-persisted regionally (1.40 %), contrasting sharply with its near absence in contemporaneous Central Plains sites (0.03 %). This trajectory underscores the resilience of regional agricultural traditions amid climatic fluctuations and their negotiated adaptation to Shang cultural expansion, as ecological constraints and imperial resource demands shaped divergent agricultural pathways. By bridging archaeobotanical data with climatic and cultural proxies, this study establishes the first empirical model of agricultural adaptation in Shang frontier zones, redefining understandings of subsistence resilience and resource politics in early territorial states.