Lactic acid bacteria will face ethanol stress when used to produce alcoholic beverages， so it is particularly important to enhance the ethanol stress tolerance of lactic acid bacteria in industrial breeding. Lacticaseibacillus casei Zhang (L.casei Zhang)， isolated from traditional koumiss in Inner Mongolia， is a probiotic strain with excellent fermentation performance. In this study， the differential metabolites between L.casei Zhang and its methylated transferase mutant were systematically analyzed by Liquid Chromatograph Mass Spectrometer (LC-MS) under 10% ethanol stress for 12 h. The aim of this study was to investigate the effects of DNA methylation on metabolites of L.casei Zhang under ethanol stress.t A total of 199 differential metabolites were identified between the methylated transferase mutant and the wild-type. Further enrichment analysis showed that the differential metabolites were mainly enriched in amino acid metabolism， ABC transporters， two-component system and pyruvate metabolism pathways. These findings have important implications for industrial breeding of lactic acid bacteria.