In the previous study, we demonstrated that ginsenoside $Rb_1$ isolated from the butanol fraction of the head of Panax ginseng had significant gastroprotective activity on gastritis and gastric ulcer models in rats. It has been well established that drugs to have capacity of scavenging or inhibiting the generation of reactive oxygen radicals prevent the gastric mucosal injury. Ginsenoside $Rb_1$ was tested on HCl ethanol-induced gastritis in rats, DPPH-induced free radical scavenging effect, MDA assay, GSH activity, and SOD activity in gastric tissue. It showed significant inhibition in HCl ethanol-induced gastritis, and al~o significantly increase of GSH activated SOD. We speculate that the protective effect of ginsenoside $Rb_1$ against HCl ethanol-induced gastric mucosal damage is originated from the increase of GSH and the activation of SOD.