Purpose- The purpose of this research is to define the concept of a mega event and analyze the trend of mega event research on published article in KCI tourism journals and provide future research directions. Design, data, and methodology- A total of 123 articles, which were related to Mega Event, Olympics, World Cup and World Fair(EXPO) were collected for the content analysis. Result- Findings showed that researches on the mega event were much performed, but a few studies have identified mega event. On the basis of a review of existing definitions, this paper defined a mega event as follows: events of huge investments at the central government, involving countries around the world, having a transformative effect on the hosting city, and attracting all of the world people. The results of content analysis revealed that mega events have been studied mainly on three subjects as national image, event impact, and visitor behavior. Conclusions- Finally the discussion proposes more arguments on the concept of mega event and on the subject of study.