The invention discloses a plant extract, specifically traditional Chinese medicine chenopodium ambrosioides extract and the agents containing the extract. The chenopodium ambrosioides extract in the invention is prepared with conventional volatile oil extraction method, the preparation methods including of its agents includes: a. extracting active ingredients from chenopodium ambrosioides throughconventional extraction method; b.adding pharmaceutical acceptable excipients and preparing agents with conventional preparation method. The chenopodium ambrosioides extract in the invention can be used to treating gastritis, gastric ulcer and other digestive system diseases caused by Helicobacter pylori-induced gastritis, and raw materials is easy to getting, preparation technology is simple, curative effect is significant and side effects is small.