Mega-event　has　received　growing　attention　as　it　brings　great　economic　benefit　to　the　host　country　or　city.　However,　Macro-economic　approach　is　the　main　method　used　in　current　researches.　Based　on　2008　Olympic　Games　in　China,　this　paper　researches　on　both　short-term　and　long-term　Microeconomic　impact　of　Mega-event,　using　event　study　method　and　trend　analysis.　Employing　the　financial　data　of　listed　company　that　are　affected　by　Olympics,　the　research　found　that　successful　bid　for　the　2008　Olympic　Games　brought　more　distinct　stimulating　effects　than　the　games　period　did,　and　related　companies　received　long-term　effects　on　profit.　The　conclusion　is　that　the　economic　impact　of　Olympics　is　limited　from　the　viewpoints　of　Micro-economy,　which　also　fits　to　economic　assessment　of　Mega-event　in　the　case　of　a　larger　economic　scale　and　helps　to　make　suggestions　for　managers　and　participants　of　Mega-event.　©　2010　IEEE.