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Boron resources are abundant in the Da Qaidam Salt Lake of the Qaidamu basin in China, which has generated significant attention due to the presence of polyborate species in brine from this lake. In this study,Raman spectroscopy was used to investigate the existing form of boron in brine dur-ing evaporation. MgO·2B 2 O3 - H2 O,MgO·2B 2 O3 - MgCl2 - H2 O,and MgO·2B 2 O3 - MgSO4 -H2 O solutions were also studied to determine the influence of boron concentration,pH,and electrolytes on the borate speciation from brine. The mononborates B(OH) 3 and B(OH)-4 were found to be the only forms present in natural salt lake brine. Brine evaporation promoted the formation of the polyborate ani-ons B3 O3 (OH)-4 ,B 5 O6 (OH)-4 ,and B 6 O7 (OH)2 -6 and also promoted the disappearance of the B(OH)-4 ion from brine at boron concentrations of more than 11 g / L B2 O3 . The pentaborate ion B5 O6 (OH)-4 was sensitive to the solution pH and appeared only at pH values less than 8. 0. Mean-while,the hexaborate ion B 6 O7 (OH)2 -6 was observed to be more dependent on the electrolyte magnesi-um chloride due to its special properties,such as promoting boron accumulation,lowering solution pH, and also its strong affinity for water molecules,which were all beneficial for the polymerization of borate ions in brine. Interaction mechanisms between polyborate anions during evaporation are also proposed herein. ake;evaporation;polyborate species;interaction mechanism.