Magnetic storms usually cause significant departures of thermospheric O and N2 from their normal values. To study the effects on thermospheric neutral species caused by magnetic storms, a method to retrieve thermospheric O/N2 based on the data obtained from global ultraviolet imager on board TIMED is presented. With the help of AURIC, the normalizations of observing angles and SZAs were preformed to the measurements and a relationship between 135.6/LBHs and O/N2 was established. Finally, applying the proposed method to retrieve O/N2 during a magnetic period（29, September—4, October, 2002）, it was shown that magnetic storms could induce significant O/N2 depletion, extending from the polar regions towards the equator.