Humic acid (HA) was extracted by NaOH solution from black soil of Heilongjiang in China.Reaction characterization of rare earth elements (La3+,Ce3+,Gd3+and Y3+) with HA was studied by Fourier transform infrared (FTIR) spectroscopy.Results showed that peaks (1600 cm-1 and 1400 cm-1) in FTIR spectra of HA became strength after reaction,implying that carboxyl groups of HA reacted with rare earth elements.