Objective：To investigate the maternal metabolome on serum and hair associated with gestational diabetes mellitus（GDM） and to explore the potential biomarker of GDM. Methods：A total of 49 GDM cases and 44 controls were recruited at 26 to 28 weeks of gestation. The serum and hair metabolomes were analyzed using gas chromatography-mass spectrometry（GC/MS） and liquid chro－matography-mass spectrometry（LC/MS）. Results：Of the 747 metabolites identified in serum and 545 metabolites identified in hair，23 and 31 were significantly different between GDM and control，respectively. For example，Amphibine H（P=0.001），N-Oleoyle－thanolamine（P=0.005），3，4-Methylenepimelic acid（P=0.043），25-Methyl-21-tritriacontene-1，9，11-triol（P=0.004） were increased in GDM. For instance，piperic acid（P=0.029），2，2，9，9-Tetramethyl-undecan-1，10-diol（P=0.017），Lenticin（P=0.004），Docosahex－aenoyl Ethanolamide（P=0.021） were decreased in GDM. And of the all significant metabolites，N-Oleoylethanolamine had the greatest ability to classify GDM status，with area under the receiver operating characteristic curve of 0.846（95%CI=0.757 to 0.920，P=0.005）. Conclusion：Metabolomics can assist with the elucidation of metabolic mechanisms underpinning GDM development. The metabolite（N-Oleoylethanolamine） that could classify GDM status was identified in the hair of participants；highlighting the potential of maternal hair as a source of biomarkers.