Cadmium　(Cd)　is　an　extremely　toxic　metal　commonly　found　as　an　environmental　contaminant　from　industrial　and　agricultural　sources,　posing　severe　risks　to　human　health.　In　this　study,　the　binding　mechanism　of　Cd(II)-human　serum　albumin　(HSA)　complex　and　the　effect　of　Cd(II)　on　the　conformational　stability　and　structural　state　of　HSA　were　comprehensively　investigated　through　a　series　of　efficient　and　appropriate　methods.　X-ray　photoelectron　spectroscopy　accurately　described　the　microenvironmental　changes　around　protein　C,　N,　and　O　atoms　in　the　presence　of　Cd(II).　Fluorescence　results　indicated　that　the　probable　mechanism　of　Cd(II)-HSA　interaction　is　a　static　quenching　process.　Fourier　transform　infrared　spectroscopy　and　dynamic　light　scattering　showed　Cd(II)　complexation　altered　HSA　conformation　and　the　microenvironments　of　Trp　and　Tyr　residues,　accompanied　by　the　size　increases　of　HSA　aggregates.　This　research　will　be　helpful　for　understanding　the　toxic　effects　of　Cd(II)　on　protein　function　in　vivo.　[Figure　not　available:　see　fulltext.]　©　2014　Springer-Verlag　Berlin　Heidelberg.