In this study, we alalyzed the relationship between the time-variation trend of air pollution concentration index and the meteorological conditions with CO(carbon monoxide) concentration and meteorological observation data in high-CO episode days. CO is a representative automobil air pollutant. The results are as follows; 1. Most of the high-CO episode days within 30 classes appeared in winter season. 2.Most of them appeared under the surface weather conditions with east-west high-pressure system. The surface winds in this high-pressure area were very light. 3. The high-CO episode days were due to unusual accumulation within urban atmosphere in the morning. 4.The Atmospheric stabilities were more stable, and then the wind-ventilation conditions were worse than yearly mean atmospheric condition in Daegu.