**Abstract**

An ethnobotanical study of medicinal plants used by the Tay ethnic group in Thai Nguyen province, Vietnam has been carried out in the present study, especially in the region of Đinh Hoá, Phú L ̣ ương, and Võ Nhai districts. The ethnobotanical survey was conducted between 2018 and 2021 and a catalog of the medicinal plant used by the Tay ethnic group is prepared. The results of the current survey revealed that the plants used by Tay ethnic group consist of 321 species belonging to 253 genera and 103 botanical families. Majority of the plants belonging the family Euphorbiaceae (20 species), Asteraceae (19 species), Acanthaceae and Rutaceae (13 species each), Fabaceae (12 species), and Poaceae (11 species). Leaves were the most frequently used plant part (48.0%) in the preparation of medicines. The most frequent preparation method was decoction (47.7%), followed by crushing (29.9%), sauna (18.0), pickle wine (11.8%), and raw (5.6%). The major plant used by Tay ethnic people were *Schefflera heptaphylla* (L.) Frodin and *Plantago major* L., (2); *Elephantopus scaber* L. and *Achyranthes aspera* L.; *Streblus asper* Lour. We also carried out screening of some of the medicinal plant extracts for their biological activities especially the inhibition of cancer cell lines.

**Keywords:** medicinal plants, Tay ethnic group, traditional knowledge, biological activities, conservation, Thai Nguyen
