Chronic atrophic gastritis (CAG) is a critical initial step in gastric cancer tumorigenesis accompanied by high malignancy. Erianin has been proposed as a promising agent in treating precancerous lesions of gastric cancer. Considering that little work has been implemented concerning the specific role and possible regulatory mechanism of Erianin in CAG, the goal of the study is to disclose the effects and mechanism of erianin on the malignant transformation in the process of CAG. CAG cell model was generated in human gastric epithelium GES-1 cells induced by Nmethyl-N'-nitro-N-nitrosoguanidine (MNNG). CCK-8 method determined cell viability. ELISA and corresponding assay kits severally appraised the contents of inflammatory cytokines and oxidative stress markers. Cellular reactive oxygen species (ROS) formation was measured by flow cytometry analysis using DCFH-DA probe. GFP-LC3 immunofluorescence staining and Western blotting evaluated autophagy. Also, Western blotting analyzed the expression of components in mitogen activated protein kinase (MAPK)/mechanistic target of rapamycin (mTOR) signaling. The results manifested that MNNG treatment diminished the viability and autophagy whereas intensified the inflammation and oxidative stress in GES-1 cells, which were all reversed by Erianin. Besides, Erianin blocked mTOR/MAPK signaling in MNNG-exposed GES-1 cells. Autophagy inhibitor 3-methyladenine (3-MA) or p38 MAPK agonist asiatic acid partially counteracted the protection elicited by Erianin against viability loss, inflammatory reaction as well as oxidative stress in MNNG-induced GES-1 cells. Combined with the findings, Erianin might mediate autophagy to improve MNNG-elicited CAG via MAPK/mTOR signaling.