A new technology of multirectification coupling extraction was applied to prepare essential oils of red onion. The chemical components in the oils were separated and identified by gas chromatographymass spectrometry hyphenated method (GCMS) combined with computer search system. The yield of onion essential oils obtained by the new technology was 0.033 mL/kg. Fourteen compounds were determined, representing 70.2% of the total oil. Sulfides were the main flavor components in the prepared onion essential oils (w=62.1%). And the content of the sulfide compounds in the dry substances was higher than 0.189 g/kg. In addition, small amounts of ketone and aldehydes were found in the onion essential oils. The yield and content of sulfide compounds of onion essential oils are two factors which should be considered when a technology is evaluated. In this paper, essential oils in red onion can not be obtained by single rectification. The results showed that different onion varieties and extraction methods would significantly influence the yield and content of volatiles flavor co mponents of onion essential oils.