This research examines the manifestation of Appreciation system in online tourism advertising discourse. The data is picked out from ten advertisements posted on Youtube by Expedia Group, an American travel group and are qualitatively and quantitatively analysed with the help of the Concordance AntConc software. The findings show that three subcategories of Appreciation which are Reaction, Composition and Valuation coexist in this discourse with different distribution. Besides, positive Appreciation and its negative counterpart are unevenly distributed in the samples, with the rate of 1: 9. Negative Appreciation, however, contributes to the ignition of visitors’ curiosity and desire to discover the destinations rather evoke unfavourable views of the appraised. Besides the conclusion, some implications for applying the research result to English teaching and learning in Vietnam are also provided at the end of the paper.