In past, parking lot was placed on the ground and for the reason air quality was not in problem. But recently parking lot has been placed under the ground and the air quality becomes problem. So in this study, the ventilation performance on the underground parking lot was estimated by using CFD software and alternative system was suggested. Three case studies are handled in this study. 1st case is just an underground parking lot. 2nd case is about an underground parking lot where has 4 fan rooms on each floor and 3rd case is about an underground parking lot where has 4 fan rooms and 30 guidance fans on each floor.