〔Abstract〕 ObjectiveTo investigate the effect of honokiol on proliferation, apoptosis, migration, and invasion of gastric cancer cells and its underlying mechanistic. Methods Human gastric cancer cell lines HGC-27 and AGS were treated with Honokiol at concentrations of 0, 15, and 25 μmol/L. CCK-8 assays were conducted to determine the half maximal inhibitory concentration (IC 50) for both cell lines. Cell viability, proliferation, migration, and invasion capabilities were assessed using CCK-8, colony formation, wound healing, Transwell migration and Transwell invasion assays. Apoptosis rates were measured via flow cytometry. Western blot analysis examined proteins related to proliferation, apoptosis, migration, invasion, and the endoplasmic reticulum stress pathway ATF4-CHOP-TRIB3. Results Compared with the control group, treatment with 15 and 25 μmol/L Honokiol significantly reduced the proliferation, colony formation, migration, and invasion capabilities of the two gastric cancer cell lines, while significantly increasing the apoptosis rate ( P< 0.05). Additionally, compared to the control group, the protein expression levels of neural cadherin（N-cadherin）, Vimentin, proliferating cell nuclear antigen（PCNA）, and B-cell lymphoma/leukemia-2 protein（Bcl-2）decreased in the two gastric cancer cell lines after treatment with 15 and 25 μmol/L Honokiol, while the protein expression levels of epithelial cadherin（E-cadherin）, Bcl-2-associated X protein（Bax）, activating transcription factor 4（ATF4）, endoplasmic reticulum stress-related protein（CHOP）, and tribbles homolog 3（TRIB3）increased（ P < 0.05）. Conclusion Honokiol promotes apoptosis and inhibits proliferation, migration, and invasion of gastric cancer HGC-27 and AGS cells by regulating the ERS signaling pathway ATF4/CHOP/TRIB3.