To pay attention to importance of earthquake prediction, many of researchers try to predict this natural disaster by means of events and precursors that take place before earthquake. Change of radon concentration in thermal waters about active faults is one of these precursors. Radon in water (especially in continues monitoring) can be determined by measuring radon in an air circuit coupled to the water. In this research used bubbling Systemfor coupling of air andwater, theoretical and empirical study are done on this system. Time constant parameter as an indictor of separation rate was lesser than 20 minutes in most of experimental conditions. In other to determine of bubbling systemÂs optimum working point, mathematical modeling of this system was presented, too.