The present study aimed to investigate the protective mechanism of N-acetylcysteine (NAC) against gastric ischemia /reperfusion (GI/R) injury in rats. After intravenous injection (IV) of NAC (150 mg/kg) into femoral vein, the rats were subjected to 30 min of ischemia induced by clamping the celiac artery followed by 60 min of reperfusion. After the gastric mucosal damage index (GMDI) had been calculated, gastric mucosal cell in situ apoptosis was detected by TUNEL method. The protein expression of p-ERK, p-JNK and NF-kappaB, and mRNA expression of TNF-alpha and Caspase-3 in gastric mucosa were evaluated by using Western-blot or RT-PCR, respectively. The results showed that NAC not only attenuated the GI-R injury, but also decreased gastric mucosal cellular apoptosis. Furthermore, NAC increased the protein expression of p-ERK, while inhibited protein expression of p-JNK, NF-kappaB in gastric mucosa. NAC also decreased the expression of TNF-alpha mRNA and Caspase-3 mRNA in gastric mucosa. Capsazepine (CPZ) (400 mg/kg, IV) reversed the protective effect of NAC against GI/R injury in rats. These results suggest that NAC can protect rats against GI/R injury. This protective effect is possibly mediated by the up-regulation of p-ERK and down-regulation of p-JNK and NF-kappaB. In addition, vanilloid receptor subtype 1 may be involved in the protective mechanism of NAC against GI/R injury.