In this study, the performance of two hybrid ventilation systems were evaluated in terms of the balance of air supply and the stability of exhaust airflow rate. The crawl space under the first floor and the natural ventilation opening were introduced an air supply system. From the results of field measurement and the calculation about the hybrid ventilation system controlled by the temperature difference, the amount of infiltration airflow rate on the second floor increases according to the rising of the crawl space temperature and the reduction of the opening area of air inlet on the first floor. The hybrid ventilation system controlled by a pressure difference sensor was introduced as an alternative to rectify the instability of the exhaust airflow rate of the former system. The stability of exhaust airflow rate and the balance of air supply were obtained at the same time from the results of measurement.