A Fourier transform ion cyclotron resonance mass spectrometry combined with electrospray ionization source(ESI FT-ICR MS) method was applied to detect the groundwater.Benefitted from the high precision molecular weight，three categories of Oxand N1Ox and N2Ox were identified，which are composed of a total of 27 heteroatomic compounds classes.Ox are dominant in these classes that nitrogen compounds combining with several O atoms are widely existed.Depending on the distribution pattern of equivalent double bond(DBE) and carbon number of heteroatomic compounds，large amounts of carboxyl were found to be present in Ox and nitrogen compounds were speculated to be derived from Ox.This work has broadened the understanding of soluble organic matter in groundwater and laid a foundation for the further research on its molecular structure.