Postural balance, which has a big role in daily life, is generally known as one's strength to retain stability. Balance takes advantage of the integration of multisensory inputs that work together to stabilize one's standing. Understanding the duty of each body part in postural balance has led us into modeling the human postural control system paying attention to the vestibular system in addition to other body parts and senses. Via updating the model both for the young and old adults, it is possible to mathematically understand the differences between the vestibular system of the young healthy adults and of the healthy elderly. Also, using linear control modeling, we provide quantitative predictions of the balance behavior depending on changes in sensorimotor behavior of different parts of the body and sensorimotor system. The results of this study help to understand better why the elderly tend to feel dizzy more often and why they would use other strategies compared to the ankle strategy.