Objective To explore the relationship between the decreased expression of AMP-18 mRNA and different degree of gastric cancer in rats. Methods A total of 20 healthy SD ratswere divided into 4 groups:groups A, B, C and D. A rat model of stomach cancer was established by feeding water with N-Methyl-N′-Nitro-Nitrosoguanidine (MNNG), Tween 20 and vitamin D3. The rats in the four groups were killed respectively at weeks 14, 18, 22 and 24. Then gastric antrum mucosa tissues were detected by using HE staining to observe the pathological changes and by real-time quantitative PCR (Q-PCR) technique to detect the expression of AMP-18 mRNA in rats. Results HE staining section showed that group C developed early gastric cancer, and group D developed progressive gastric cancer. The expression of AMP-18 mRNA in groups C and D wassignificantly lower than that in group A by Q-PCR. Conclusion AMP-18 mRNA expression decreased obviously in early orprogressive gastric cancer.