China has become the world No 1 tea producing country and accounts for more than 1/4 of the world total tea output.Especially, Chinese green tea is the globally dominant product, occupied about 75% of the green tea market, while the scientific research on tea aroma is still limited particularly in China.Generally the volatile compounds of tea are quite complicated and in trace level (around 0.1% in total).The topnote of tea usually contains 40 to 100 main ingredients.It is an analytical challenge to have qualitative and quantitative information of these volatile constitutes.