A new abietane diterpenoid glycoside, ajugaside B (1), along with three known compounds (2-4), were isolated from the whole plants of Ajuga ovalifolia var. calantha. The structure of the new compound (1) was elucidated by means of spectroscopic analyses (HRESIMS, IR, NMR and ECD). All of the isolated compounds were evaluated for their antitumor activities against MGC803, MCF-7, A549, HT29 and HepG2 cell lines. Compounds 3-4 showed moderate cytotoxicity against all tested cell lines with IC50 values of 1.8-7.3 μM.