Abstract: Objective: To investigate the bactericidal mechanism of a composite sol made of carbon nitride and chitosan on Salmonella typhimurium by studying its effects on lipid metabolism. Methods: Transmission electron microscopy and protein leakage concentration were utilized to evaluate the magnitude of cell membrane damage induced by carbon nitride-chitosan composite sol at a cellular level. In addition, lipid metabolomics was employed to investigate the bactericidal process by examining several metabolite functions and regulatory networks associated with bacterial lipid metabolism. Results: The composite sol of carbon nitride-chitosan caused more extensive damage to the cell membrane of Salmonella typhimurium. In lipid metabolism, the substantial up-regulated in 203 metabolites and down-regulated in 95 metabolites were observed. These metabolites were particularly involved in the metabolism of fatty acids, glycerophospholipids, and glycolipids, which play an important part in maintaining the integrity of cell membranes. Metabolite function analysis showed that the composite sol treatment disrupted various metabolic pathways in bacteria. These pathways include fatty acid biosynthesis, glycerol phospholipid metabolism, linoleic acid metabolism, tetraenoic acid metabolism, as well as pathways related to cell energy metabolism, material transport, and signal conduction. These disturbances finally resulted in the demise of the bacteria. Conclusion: This study reveals from the perspective of lipid metabolism that the combination of carbon nitride and chitosan disrupts the metabolic pathways of Salmonella, especially those related to lipid metabolism, leading to bacterial metabolic disruption and death. It provides a theoretical basis for comprehending the mechanisms by which photocatalytic materials exert their antibacterial properties.