Radon, which is one of the radioactive elements in the natural world, exists in the atmosphere and water. When this element inflows into the human body, it carries the risks of developing lung cancer and stomach cancer. Therefore, in this study, an effective 10 L scaled reactor was produced to mitigate radon in water and the radon mitigation efficiency in water following the changes in water temperature and amount of aeration were evaluated. Based on this, the radon mitigation efficiency (SRRR; Specific radon removal rate) was derived per unit air volume. According to the study result, when water temperature increased from $10^{circ}C$ to $16^{circ}C$, the SRRR value increased from 95 $nCi/m^3{cdot}L$ to 134.4 $nCi/m^3{cdot}L$, and when the amount of aeration increased from 0.2 L/min to 1 L/min, the SRRR value decreased from 198.1 $nCi/m^3{cdot}L$ to 72.2 $nCi/m^3{cdot}L$. Therefore, based on the experimental results, it is considered that it can be applied as a examination factor and objective indicator during the design of future radon-in-water mitigation systems.