The loads of ventilation systems in underground subway stations are time-varying since the subway schedule of rush hour (morning and evening), and ordinary time zone is varied in stations according to time zones. The objective of this study is to develop a real-time energy-efficient ventilation control strategy based on the real option of time-varying ventilation loads for the periodic variations of indoor air quality (IAQ) in a subway station. The experimental results from an underground subway platform showed that the proposed ventilation control method with 6 hours time interval could reduce the ventilation energy by 3%, compared to the ventilation energy with manual control while maintaining a healthy and comfortable IAQ level.