Abstract: Objective: To determine the expression of TNF-α protein and mRNA in rat gastric mucosal cell during small dose aspirin induced gastric mucosal injury and its significance. Methods: By immunohistochemistry and RT-PCR method, we examined the expression of TNF-α in gastric mucosal cell. Results: TNF-α started to express at 15min after administration of aspirin, peaked at 3h,decreased at 12h, remained at 24h in experiment group. The expression of TNF-α decreased significantly after administration of aspirin compaired with that before administration of aspirin in experiment group There is lower level expression in control group and preced disposed group than in experiment group. There is no obvious diffirence betweencontrol group and preced disposed group Conclutions: The expression of TNF-αplays an important role in the mechanisms ofsmall dose aspirin induced gastric mucosal injury.