Two unreported sesquiterpene chromones, (±)-ferulasin (1), were isolated from the roots of Ferula sinkiangensis. Ferulasin (1) shows one uncommon oxygen-containing macrocyclic structure with one trioxaspiro, and represents a new framework in which the side chain sesquiterpene C-100 and C-110 form an oxygen-containing 13-membered ring with chromone C-2. The chemical structure was established by diverse spectroscopic methods, X-ray crystallographic analyses and ECD calculations. (±)-Ferulasin (1) exhibited potent cytotoxicity against pancreatic cancer cells with IC50 values ranging from 0.92 ± 0.12 to 19.13 ± 2.99 mM.