This study took instant Lentinus edodes (L.edodes) soups as the research object to analyze the effects of steam reheating and microwave reheating methods on the flavor characteristics of L.edodes soups using electronic nose and gas chromatography-ion mobility spectrometry (GC-IMS). The results from electronic nose showed that the odor characteristics of L.edodes soups after reheating changed significantly (P<0.05). By GC-IMS analysis, 56 volatiles compounds including some dimers of flavor compounds were both identified in L.edodes soups before and after reheating. And the varieties of flavor compounds were same, but the contents were significantly varied. The contents of ocimene, octanal and its dimer, heptanal and its dimer, 2-cyclohexen-1-one, 2-furfural and its dimer, pentanal and its dimer and 2-methylpropanal in microwave reheating L.edodes soups were higher than those of steam reheated and unheated L.edodes soups. The contents of dimethyl trisulfide, p-cresol, dimethyl disulfide, 5-methyl-2-furfural, 1-hexanol and its dimer in steam reheating L.edodes soups were higher than those of microwave reheated and unheated L.edodes soups. Collectively, the reheating treatment had a greater influence on the volatile flavor substances of the L.edodes soups, and the contents of the volatile flavor substances in the reheated L.edodes soups were higher.