Magnesium (Mg) isotopic compositions help decode the complex biogeochemical cycling of Mg in surficial environments. Accurate measurement of Mg isotopes in biological samples requires reference materials with established isotopic compositions, which ensure analytical quality and allow interlaboratory comparison. By employing Nu Plasma III multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS), this study establishes a high-precision Mg isotopic dataset for sixteen biological reference materials. The measured δ26Mg values of extra nine reference materials (plant leaves, rocks, and seawater) consistently agree well with references values, confirming the reliability of analytical methodology used in this study. The results reveal the variations for δ26Mg values exceeding 2.2‰ across the food web. Plant leaves are characterized by low δ26Mg values (–0.52‰ ± 0.04‰ ~ –1.28‰ ± 0.03‰), whereas cereals and animal organs exhibit heavier values (up to 0.97‰ ± 0.05‰ for pork liver). The δ26Mg values of scallops (GSB-15), spirulina (GSB-16), and prawn (GSB-28) cluster together with lighter values, representing a marine-derived isotopic end-member for coastal populations. Human hairs (–0.88‰ ± 0.04‰) present an integrated isotopic signature intermediate between major dietary end-members. This dataset expands the Mg isotopic compositions of major dietary and human tissue reference materials, supporting the essential laboratory comparison of isotope analyses and facilitating researches into the Mg biogeochemical cycle.