A peak including an unknown component in the total ion chromatogram of essential oil from Citrus reticulata Blanco peel, which retention index is nearly the same as that of tetradecanoic acid (1748) in apolar column, can’t match a suitable compound through the searching of NIST08 (National institute of science and technology) MS (mass spectrum) database. Its’ structure was tentatively elucidated by the mass spectrum. In the end, the most probably identity was deduced, and its correction will be confirmed in the following research.