Sambucus simsponii Rehd, Clematis brevicaudata DC., Euodia lepta (Spreng) Merr., and Hedyotis capitellata Wall. ex G. Don. var. mollis (Pierre ex Pit.) are commonly used medicinal plants in the traditional herbal remedies of the Red Dao ethnic group. In this study, leaf samples of the four herb species were collected, classified, extracted, and evaluated for their impact on cell division using MTT assay, as well as on cell morphology using DAPI staining method. The experiments were conducted on the gastric cancer cell line AGS. The research results showed that Sambucus simsponii Rehd exhibited the strongest inhibitory effect with an IC50 value of 8.21 µg/mL. Hedyotis capitellata Wall. ex G. Don. var. mollis (Pierre ex Pit.), Euodia lepta (Spreng) Merr., and Clematis brevicaudata DC. had IC50 values of 26.06 µg/mL, 31.0 µg/mL, and 52.45 µg/mL, respectively. The extracts from all four herbal medicines were able to induce changes in cell morphology and nuclear morphology. The extracts from these herbal medicines induced the formation of apoptotic cell morphology, leading to programmed cell death in the AGS gastric cancer cells under different culture conditions. This research result showed that all four herb species used by the Red Dao people in this study have potential to inhibit AGS gastric cancer.