Fatty acid synthase (FAS) is considered as a novel drug target for the development of anticancer and anti-obesity agents. Bioassay-guided fractionation of a n-hexane-soluble extract prepared from the roots of Salvia miltiorrhiza Bunge (Labiatae), using an in vitro enzyme assay, led to the isolation of five abietane diterpenoids: 15,16-dihydrotanshinone I (1), cryptotanshinone (2), tanshinone I (3), tanshinone IIA (4), and dansenspiroketallactone (5). Compounds 1-5 were tested for their in vitro FAS inhibitory activity and, except for compound 5 ($IC_{50}$ > $100{mu}M$), compounds 1-4 inhibited the enzyme activity with $IC_{50}$ values ranging from 12.0 to $30.3{mu}M$. Our findings may be partIially related to the anticancer activity of abietane diterpenoids from the plant, suggesting a further study on the anticancer potential of tanshinone derivatives.