Abstract In this work, the toxic influence of metallic ions (Na +, Cu 2+, Al 3+) on the serum albumin were studied by fluorescence, resonance light scattering (RLS), synchronous fluorescence, UV–vis absorption and circular dichroism (CD) spectroscopy. The experimental results indicated that ion electric charge is not the main factor affecting the structure of bovine serum albumin (BSA). Na + made the structure of BSA tighter and hydrophobicity enhanced, which improved fluorescence intensity, while Cu 2+ could react with some functional groups of BSA, making the structure of BSA looser, so that the internal hydrophobic groups such as tryptophan (Trp) and other aromatic residues were gradually exposed. When we observed them with fluorescence spectra, we found fluorescence quenching with increasing Cu 2+ dose. Al 3+ is shown as little significant influence on the BSA, but BSA was found to aggregate with the dose of Al 3+ by means of RLS because of the hydrolysis and ion strength effect of Al 3+. The results also proved normal saline could keep lives healthy and good-working as a biological humour, however, heavy metals made harmful effects to the body when they exceeded the minimal effect level (MEL), such as Cu 2+ chosen in our work.