In the present paper, the hydrophobicity ionic liquid 1-butyl-3- methylimidazolium hexafluorophosphate (［C4mim］［PF6］) was synthesized with 1-methylimidazole and butylbromide and equimolar ammonium hexafluorophosphate, which was applied to preconcentration for trace gold. The factors which may affect preconcentration of gold were investigated. The experimental results showed that the absorbance was linear when the concentration of gold was in the range of 0.40~16.00μg·mL-1, with linear equation A = 0.007 63c +0.073 87(c:μg·mL-1), correlation coefficient r = 0.999 1, and detection limit 0.072 μg·mL-1. The method was applied to the determination of trace gold in water samples satisfactorily.