Abstract: In order to understand the concentration characteristics of VOCs species emitted from crude oil refinery,VOCs were sampled at the boundary of a refinery from May to September in 2011 by using SUMMA canisters,and then were analyzed by gas chromatography-mass spectrometry(GC-MS) to get the mixing ratio of each VOC in the boundary area in spring,summer and autumn.Finally,about 50 VOCs species were detected,C3-C8 hydrocarbons accounting for more than 80% of the total VOCs in volume,in which alkenes with the volume contribution of more than 50%.In addition,maximum increment reactivity(MIR) was used to quantify the ozone formation potential of various VOCs species emitted from the refinery.The results showed that although the volume percentage of alkanes was much higher than that of alkenes in the refinery boundary,alkenes had the maximum photochemical ozone formation potential,which contributed over 53% in the ability of ozone formation by all VOCs sepcies.