The interaction of bovine serum albumins with cetyltrimethyl ammonium bromide was studied by means of the two-dimensional infrared correlation spectroscopy. The results showed that the secondary structures of bovine serum albumins were changed when cetyltrimethyl ammonium bromide was added and the changing sequence is β-sheet, β-strand, α-helix with the increase of cetyltrimethyl ammonium bromide.