Boron is difficult to be removed from seawater by simple RO (reverse osmosis) membrane process, because the size of boric acid (B(OH)3), the major form of aqueous boron, is as small as the nominal pore size of RO membrane. Thus, the complexation of boric acid with polyols was suggested as an alternative way to increase the size of aqueous boron compounds and the complexation behavior was investigated with Raman spectroscopy. As a reference, the Raman peak for symmetric B-O stretching vibrational mode both in boric acid and borate ion (B(OH)4 -) was selected. A Raman peak shift (877 cm-1 →730 cm-1) was observed to confirm that boric acid in water is converted to borate ion as the pH increases, which is also correctly predicted by frequency calculation. Meanwhile, the Raman peak of borate ion (730 cm-1) did not appear as the pH increased when polyols were applied into aqueous solution of boric acid, suggesting that the boric acid forms complexing compounds by combining with polyols.