Objective To investigate the effects of sodium butyrate (SB) on fetal gastric epithelial cells (GECs) in vitro damaged by N-methyl-N’-nitro-N-nitrosoguanidine (MNNG). Methods The fetal gastric epithelial cells were isolated, cultured and identified. Then the cells of the second generation were cocultured with 10 -5 mol/L, 10 -6 mol/L, 10 -7 mol/L SB for 4 h, then added with 10 -5 mol/L MNNG culturing for another 24 h. After the treated cells were finally cultured in normal culture medium for 40 d, the unscheduled DNA synthesis (UDS), lipid peroxidation (LPO) and ras p21 were detected. The cells were only cultured with 10 -5 mol/L MNNG served as negative control and without MNNG or SB as normal control. Results The level of UDS, the contents of lipid peroxidation products and the concentrations of ras p21 in GECs treated with 10 -5 mol/L and 10 -6 mol/L SB decreased obviously, and had significant differences with that of GECs treated without SB. Conclusion SB can effectively prevent the damage of GECs induced from MNNG.