To investigate the formation mechanism of the characteristic ‘fungus aroma’ in Fu brick tea, Using the same fresh leaf raw material were used to produce both Fu brick tea and white brick tea. Artificial inoculation with Eurotium cristatum was performed under two conditions: monofungus fermentation by artificial inoculation (inoculated only with Eurotium cristatum) and traditional fermentation. Metabolomics was employed to analyze the dynamic changes of key aroma compounds associated with the " fungus aroma" note. Combined with transcriptomics, the gene expression profile of Eurotium cristatum during monofungus fermentation was further investigated. The results indicate that levels of key alkenal compounds, including (E,E)-2,4-heptadienal, (E,E)-2,4-nonadienal, and (E,Z)-2,6-nonadienal, in Fu brick tea are significantly higher than those in white tea bricks. The content of alkenal compounds significantly increases in the later stage of traditional fermentation, while the content of unsaturated fatty acids, the precursor substances of alkenal compounds, increases in the later stage of monofungus fermentation. The possible reason is that the metabolic pathway for generating alkenal compounds is inhibited during the flowering process. Transcriptome sequencing indicated that during the fermentation process with Eurotium cristatum, fatty acid consumption was reduced, leading to their accumulation. Moreover, the alpha-linolenic acid metabolic pathway in Eurotium cristatum was not annotated with lipoxygenase, suggesting that this fungus cannot generate di-unsaturated aldehydes via the lipoxygenase oxidation pathway. This may explain why the levels of (E,E)-2,4-heptadienal and (E,E)-2,4-nonadienal in monofungus fermentation tea were significantly lower than those in traditional fermentation. Consequently, monofungus fermentation alone fails to develop the characteristic fungal aroma. In the complex environment of traditional fermentation, will be signal transmission and material exchange among other microorganisms. They can convert the unsaturated fatty acids produced into alkenal compound by Eurotium Cristatum. Therefore, the formation of ‘fungus aroma’is achieved through the synergistic fermentation of the basic aroma of raw dark tea and the Eurotium Cristatum community.