Abstract: Tumor immune therapy has been remarkably successful in recent years and several kinds of PD-1/PD-L1 (programmed death-1/programmed death-ligand 1) antibody drugs have been approved by the FDA for treatment of advanced malignant neoplasms. However, as biomacromolecules these antibody drugs have certain drawbacks such as high cost, injection-only administration and immunogenicity; thus, we turned to small molecules that have lower immune risks and better modifiability. Considering the structural diversity of natural products, we chose to investigate the active components in Panax ginseng, a famous and highly valued traditional Chinese medicine. Nine compounds were separated and identified in this research using a HPLC-coupled MS system, and 3 PD-1 binding compounds were identified using the SPR method. The PD-1/PD-L1 inhibitory ability of ginsenoside Rg₁, as a representative ginsenoside, was verified by cytopharmacological methods. This research provides a new method for the identification of immune blockade inhibitors in natural products.