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To explore the effects of fresh leaves harvested at different picking periods on aroma quality and chemical characteristics of oolong tea, morning leaves and evening leaves of Tieguanyin were selected as materials and turned into morning tea and evening tea according to the traditional technology. The volatile components of fresh leaves and oolong tea were analyzed by the method of gas chromatography-mass spectrometer (GC-MS), in order to compare their differences between morning oolong tea and evening oolong tea. The results showed that total volatile components of evening tea were 28.3% less than that of morning tea. The content and proportion of alcohol compounds were superior, especially isophytol and trans-nerolidol. The characteristics of volatile components in fresh leaves were different from that in oolong tea. The rate of alcohol compounds was close to that of acid compounds in fresh leaves, while in oolong teas the difference was large. Two kinds of fresh leaves had 56 identical components, that were 4 more than the two kinds of oolong tea. However, among 42 common components of fresh leaves and oolong tea, palmitic acid, dihydroactinidiolide, trans-nerolidol and isophytol were obviously affected by the manufacture technology, and their variation amplitudes were large. It can be seen that the distribution characteristics of volatile compounds of evening leaves and morning ones were different, and the aroma quality of evening tea was better than that of morning tea, especially the refreshing aroma.