The paper studied the antioxidant activity and chemical composition of ether extracts of Semen Plantaginis. The antioxidant activity of ether extract was evaluated by two in vitro systems, viz. DPPH radical scavenging activity and pyrogallol autooxidation methods. The results indicated that the usage of ether extract is in directly proportion to the anti-oxidative effect. The effects of ether extract in the two systems were both existed but lower than BHT and ascorbic acid. The chemical composition of the extract was deduced from GC-MS analyse. It is found that two main components are (Z,Z)-9,12-Octadeca-dienoic acid (79.22%, the highest content) and n-Hexadecanoic acid (13.63%, second). Moreover, there have small quantities of 22,23-dihydro-Stigmasterol (1.06%), (E,E)-2,4-Decadienal (0.12%), Stigmasterol (0.09%), (Z)-2-Heptenal (0.07%), 2-Cyclohexen-1-ol (0.06%), Z,Z-10,12- Hexadecadien-1-ol acetate (0.04%) and Octane (0.03%).