The structural differences of mineral source fulvic acid(MFA)，biochemical source fulvic acid(BFA)，and straw source fulvic acid(SFA)were explored，so as to provide a reasonable basis for the application of fulvic acid in agricultural production.Technologies including elemental analyzer(EA)，ultraviolet-visible spectroscopy(UV-Vis)，fourier transform infrared spectroscopy(FTIR)，carbon-13 nuclear magnetic resonance spectroscopy(13C-NMR)，three-dimensional fluorescence spectroscopy(3D-EEMs)，and gas chromatography-mass spectrometry(GC/MS)were employed to study the elemental composition，functional group types，chemical structure characteristics and compound composition of different types of fulvic acids..The elemental composition showed that the content of O，S，N and H elements in SFA were higher than that in MFA and BFA，and it had higher the ratios of H/C，O/C，N/C and(N+O)/C.UV-Vis and FTIR showed that compared with MFA，BFA and SFA had weaker aromaticity，more oxygen-containing functional groups on the aromatic ring，smaller molecular weight and lower degree of polymerization. 13C-NMR showed that the carbon structure of the three types of fulvic acids were dominated by alkoxy carbon and aromatic carbon，while the hydrophobicity index and aromatic condensation degree of SFA were lower than those of MFA and BFA. 3D-EEMs showed that the three types of fulvic acids were dominated by oxygen-containing substances with carbonyl，carboxyl，and phenolic structures in terms of composition，among which the carboxyl，carbonyl，and phenolic structures of SFA and BFA accounted for a large proportion，while MFA had more aromatic structures.GC/MS found that MFA，BFA and SFA were composed of 84，93 and 101 compounds，respectively，and the main components were oxygen-containing compounds，accounting for 89.89%，92.80%，and 86.28%，respectively. The content of nitrogen-containing compounds in SFA was higher than that in MFA and BFA..In summary，there were certain differences in elemental content，oxygen-containing functional groups，chemical structure characteristics，and compound composition of different types of fulvic acid. Among them，SFA had more nitrogen- and oxygen-containing functional groups and compound compositions，smaller molecular weight，weaker aromatics and stronger activity，and it was a good alternative to MFA and BFA.