This study studied humic acid structures of the typical northern soil, i.e., black soil, chestnut soil and fluvo-aqulc soil by using elemental analyzer, Fourier transform infrared spectrometer and 13C NMR. Both the contents of various elements and functional groups in humic acids of three kinds of soils were different. H/C atomic ratio was in an order of fluvo-aqulc soil＞chestnut soil＞black soil, O/C atomic ratio was not significantly different in the three kinds of soils. C/N atomic ratio presented in an order of black soil＞chestnut soil＞fluvo-aqulc soil. The positions of the absorption peaks in infrared spectra of humic acids were similar in the three kinds of soils but different in the peak intensity, the signal intensities at 3 352 cm-1 and 2 931 cm-1 of fluvo-aqulc soil and chestnut soil were equivalent while black soil was lower; the signal intensities at 2 580 cm-1 of the three kinds of soils differed little. The signal intensities at 1 720, 1 620, 1 420 and 1 220 cm-1 were all in an order of black soil＞chestnut soil＞fluvo-aqulc soil. 13C NMR showed more polysaccharides and protein structural units contained the structure of fluvo-aqulc soil; black soil had higher organic matter and a higher degree of aromatization.