The constituents of total triterpenoids (TTs) prepared from the ultrasonic-circulating extract powder (UCEP) of Ganoderma lucidum (Lingzhi), were analyzed by liquid chromatography coupled with mass spectrometry (LC-MS) method. Approximately 56 molecular ion peaks were simultaneously acquired from the total ion-current chromatography (MS+) of TTs. Among these constituents, at least 31 precursor ions for triterpenoids were determined with m/z values of 418.3~678.5, corresponding to the molecular weight of known triterpene acids and triterpenoid saponin. The in vitro assays showed that the TTs from UCEP possessed favorable scavenging capacity for free radicals (DPPH·, ABTS·+ and O2 -) as well as total antioxidant activity (T-AOA) and ferric reducing antioxidant power (FRAP).