Abstract: Organic constituents in the sodium aluminate solution，which is the important intermediate material of the Bayer process,change evidently because of trace amount long fatty acid collector adsorbed onto bauxite concentrates entering into the Bayer process.The effects of long fatty acid collector on the structure of sodium aluminate solution was studied with plastics sheets attached water as the background of infrared spectrum.The results showed that the characteristic peaks of sodium aluminate solution was distinct.The Al—O—Al bond peak intensity increased and the Al(OH)^-₄ bond peak intensity was constant with increasing content of the collector PS.The peak intensity of Al—O—Al vibration and AlOH antisymmetric vibration was stronger in α_k=1.56，ρ_Na2O=160 g•L^-1 solution than that in α_k=3.0，ρ_Na2O=220 g•L^-1 solution.