In order to reveal the changes of free radicals during the oxidation process of vegetable oils at room temperature， this paper took four common vegetable oils as raw material， including flaxseed oil， peanut oil， sunflower oil and tea seed oil. The changes of free radicals and hydrogen spectrum were investigated by using electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) techniques. The results showed that: linseed oil， sunflower seed oil and peanut oil mainly formed alkyl free radicals (R·)， alkoxy free radicals (RO·)， alkoxy peroxide free radicals (ROO·) and other unknown free radicals (DMPO-X) when oxidized at room temperature， with different contents. The sequence of the free radical contents in linseed oil and peanut oil was DMPO-X>RO·>R·>ROO·. The content of each free radical in sunflower seed oil was sorted as RO·>DMPO-X>R·>ROO·. When camellia oil was oxidized at room temperature， three kinds of free radicals were mainly formed， and the content was RO·>DMPO-X>ROO·. The 1H NMR spectra of the four vegetable oils showed no significant changes， and the characteristic peak and peak areas changed before and after oxidation， and the four oils were in the primary oxidation stage. The process of room temperature oxidation of vegetable oils dominated by linolenic acid or linoleic acid and oleic acid， DMPO-X was mainly produced. RO· is mainly produced in linoleic acid or oleic acid-dominated vegetable oils during the oxidation process at room temperature.