In this paper, we analysed the changes of NO contents in serum and gastric mucosa in experimental ulcer rats treated by moxibustion, and observed its effect on L-NNA inhibition. The results showed:NO contents in gastric ulcer rats were increased, especially the contents of NO in gastric mucosa werehigher than that of the normal control group, P< 0. 05. After moxibustion the NO level was decreased,tending to the normal level, among them the changes of NO in serum had statistical significance, P< 0.05. By injection of L-NNA the NO contents in gastric ulcer rats showed a tendency to decrease. Aftermoxibustion no was more decressed. It suggested that NO participating in the treatment of moxibustiongastric ulcer might be due to a protection against the damage of gastric mucosa caused by the propertiesof vascular relaxation. Moreover, moxibustion could strengthen L-NNA inhibition on the synthesis ofNO