Although modified Liu Jun Zi decoction (MLD) has favorable outcomes for chronic atrophic gastritis (CAG) in clinics, the identification of its active ingredients and the molecular mechanism of pharmacology are still unknown and need to be solved urgently. In the study, we screened 170 active components of MLD based on oral bioavailability ≥30% and drug-likeness ≥0.18 via the TCMSP platform. We further establish a dataset containing 315 CAG targets from PharmGkb, GeneCard, OMIM, DrugBank database, and Therapeutic Target database. Network pharmacology found that there are 110 active components of MLD and 26 potential targets for CAG in the “ingredient-target” network. The results of gene ontology analysis show that these targets are involved mainly in reactive oxygen species metabolic process, regulation of vasculature development, and T cell activation. KEGG pathways analysis indicates that these signaling pathways in the treatment of CAG include HIF-1 signaling pathway, neurodegeneration-multiple diseases pathway, MAPK signaling pathway, and PI3K-Akt signaling pathway. Finally, docking of the active component quercetin and clinical medicine Omeprazole with the core targets was carried out. We found that quercetin, a crucial active ingredient in MLD, has good binding activity with potential targets of CAG, and its molecular conformation is stable, which is better than the binding energy of Omeprazole. So, the active ingredients of MLD exhibit good potential drugs for the treatment of CAG.