The purpose of this study is to show how large sports event effect the host city`s environment. More specifically the influence of the 1988 Olympic on the city of Seoul, Korea. This thesis will provide evidence that shows changes in the city`s natural resources (i.e. water and air), and also changes in the city`s cosmetics(i.e. roads and streets, planting of trees, making parks). The result of the study was; 1. Because of the 1988 Olympic the quality of the air improved in the city of Seoul. The processes that helped to improved the air quality were: using unleaded gasoline in automobiles, using cleaner burning gas, setting strict guide line on smog exhaust and regular smog checks, and frequent air pollution check with a Telemetering System (TMS). 2. Because of the 1988 Olympic the quality of the water improved in the city of Seoul. The processes that helped to improved the water quality were: improving the building more water purifying plants, separating industries`s waste with house hold waste, and putting strict guide line on industries` waste production and disposal. 3. Because of the 1988 Olympic the quality of the streets and roads improved in the city of Seoul. The processes that helped to improved the streets and roads were: paving and building more streets and roads for easier travel, and brighting the city by putting more lights(in 1998 almost 100% of the city`s streets and roads were paved). 4. Because of the 1988 Olympic the beauty of the city improved. The processes that helped to beautify the city were: planting more trees and making more parks. Now the city of Seoul is one of the great city of the world. This is do part by hosting the 1988 Olympic Games.