Objective To observe the changes of intestinal flora structure and abundance in mice with gastritis induced by Helicobacter pylori （HP）. The cecal contents were obtained for sequencing analysis,and the effects of long-term use of the extract of Chenopodium ambrosioides L. on mice were investigated by analyzing the changes in the structure of the intestinal flora. Methods Thirty male Kunming mice were randomly divided into blank group （n = 10）,model group （n = 10） and CAL （Chenopodium ambrosioides L.）group （n = 10）. After HP infection was established,they were administered drugs for 4 weeks,and fresh rectal stools of each group of mice were taken at the same time. The 16 S rDNA-V3-V4 region of the fecal samples was sequenced on an Illumina Hi Seq PE250 highthroughput sequencing platform to quantify the structure and abundance of the intestinal flora. Results At the level of the portal,the relative abundance of the Helicobacter pylori infection model group,such as Bacteroides, Proteobacteria, Mycobacterium, Softwalled bacteria,and actinomycetes,were decreased,and the relative abundance of the thick-walled bacteria increased in the model group. There were significant differences with the blank group and the schizonepeta group; at the genus level,the relative abundance of the model group Lactobacillus and Bifidobacterium decreased, Bacteroides, rumen cocci, dystrophic and Phytophthora,Enterococcus,increased. The relative abundance of the genus Monocytogenes was elevated. The relative abundance of Enterobacter and Limerella was increased,and the relative abundance of Enterococcus was decreased. Conclusion This study suggests that colonization of HP significantly could change the structure of the intestinal flora,and the abundance and diversity of the intestinal flora could be reduced. The pathogenesis of HP infection with gastritis may be related to the decrease of probiotics and the increase of harmful flora. Intervention of E. striata can improve the effect of HP infection on intestinal flora and increase the diversity of flora.