Abstract: To elucidate the metabolic mechanism of Enterobacter hormaechei in improving the quality of fermented tobacco leaves, non-targeted metabolomics technology was employed to systematically analyze the transformation patterns and key functional pathways of metabolites during the solid-state fermentation procedure of tobacco leaves. The high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (HPLC-QTOF-MS) technology was applied and partial least squares discriminant analysis (PLS-DA) was conducted to screen differential metabolites in tobacco leaves (C3F-AB 2022) from Baoji tobacco-producing area of Shaanxi Province fermented by Enterobacter hormaechei for 0-72 h. The key metabolic pathways were identified using KEGG pathway analysis. The results showed that: 1) A total of 945 metabolites were identified, 151 of which were significantly differential metabolites, including glucose, amino acids, organic acids, and terpenoids, etc. 2) The differential metabolites were enriched in 129 pathways, such as biosynthesis pathway of phenylalanine, tyrosine, and tryptophan and biosynthesis pathway of terpenoid and quinone. Among these, 5 pathways including biosynthesis of terpenoids and quinones, metabolism of phenylalanine and metabolism of galactose were significantly related with the leaf quality improvement. Non-targeted metabolomics analysis revealed that the growth and metabolism of Enterobacter hormaechei drive the transformation of differential metabolites by enriching in key pathways including terpenoids synthesis and phenylalanine metabolism, thereby improve the quality of tobacco leaves.