Noninvasive positive pressure ventilation (NPPV) has been widely used in the clinical and domestic therapy. Air leak is the unavoidable problem during NPPV. Undesirable leak may cause side effects on ventilation. In this paper, an experiment platform was established to study air leak in ventilation. The platform includes three parts: a ventilator control system, a lung model and a detection module. The platform was validated effective in NPPV leak study. Based on the experiment platform, the impacts of leak were studied. The air leak varied with the size of leak holes, airflow rate and airway pressure. It is found that in volume control ventilation the airflow rate about 25L/min will lead to less leakage than other airflow rates. It is significant for NPPV to establish an experiment platform and to discover the relationships between leakage and set-up parameters.