BACKGROUND: According to traditional Chinese medicine (TCM), drugs supplementing the vital energy, Qi, can eliminate tumors by restoring host immunity. The objective of this study is to investigate the underlying immune mechanisms of anti-tumor activity associated with Qi-supplementing herbs, specifically the paired use of Huangqi and Danggui. METHODS: Analysis of compatibility regularity was conducted to screen the combination of Qi-supplementing TCMs. Using the MTT assay and a transplanted tumor mice model, the anti-tumor effects of combination TCMs were investigated in vitro and in vivo. High content analysis and flow cytometry were then used to evaluate cellular immunity, followed by network pharmacology and molecular docking to dissect the significant active compounds and potential mechanisms. Finally, the anti-tumor activity and the mechanism of the active ingredients were verified by molecular experiments. RESULTS: There is an optimal combination of Huangqi and Danggui that, administered as an aqueous extract, can activate immunity to suppress tumor and is more effective than each drug on its own in vitro and in vivo. Based on network pharmacology analysis, PIK3R1 is the core target for the anti-tumor immunity activity of combined Huangqi and Danggui. Molecular docking analysis shows 6 components of the combined Danggui and Huangqi extract (quercetin, jaranol, isorhamnetin, kaempferol, calycosin, and suchilactone) that bind to PIK3R1. Jaranol is the most important component against breast cancer. The suchilactone/jaranol combination and, especially, the suchilactone/kaempferol combination are key for immunity enhancement and the anti-tumor effects of the extract. CONCLUSIONS: The combination of Huangqi and Danggui can activate immunity to suppress breast cancer and is more effective than the individual drugs alone.