Abstract Background Methyl jasmonate (MeJA) is an effective plant elicitor that enhances secondary metabolism. Chinese chives are prized for their pungent flavor, yet the biosynthetic pathways and regulatory mechanisms of flavor compounds induced by MeJA remain unclear. Methodology This study integrated metabolomic and transcriptomic analyses to elucidate how MeJA modulates the biosynthesis of flavor substance precursors in soilless-cultivated Chinese chives. Results MeJA treatment improved the dry matter content and nutritional quality of Chinese chives. We identified 36 volatile and 183 nonvolatile differentially abundant metabolites between the MeJA-treated and control groups. Gene expression analysis revealed 193 candidate genes associated with flavor formation. Among all the genes, a total of 2,667 DEGs were enriched primarily in metabolic pathways, including secondary metabolite biosynthesis, linoleic acid metabolism, and phenylpropanoid biosynthesis. Furthermore, exogenous MeJA inhibited the synthesis of endogenous jasmonic acid as well as enzyme activity and gene expression related to metabolic pathways. It also promoted the conversion of S-alkyl-L-cysteine to S-alk(en)ylcysteine sulfoxides (CSOs), increasing the accumulation of the flavor precursor CSOs and increasing the levels of S-methyl-L-cysteine. This led to increased concentrations of the key garlic flavor compounds methiin and alliin, intensifying the pungent flavor of Chinese chives. Notably, MeJA-induced AtuFMO1 was associated with enhanced pungent flavor and may be regulated by AtuPHL7 and AP2/ERF-ERF transcription factors. Conclusion In conclusion, exogenous MeJA activates key enzyme-encoding genes involved in the biosynthesis of garlic flavor precursor CSOs, leading to increased accumulation of the spicy compounds Methiin and Alliin. These findings establish AtuFMO1 as a central hub linking hormonal signaling to flavor biosynthesis and provide molecular targets for improving Allium crop flavor and quality through precision horticulture.