As the feature of fire, it is hard for deep-seated fire to spread to the deeper site, and it also has danger for being re-ignited cause of recontacting with oxygen after being put off. Now it is ruled in the certification criteria of wetting agent used for extinguishing deep-seated fire that the criteria for surface tension is below 33[mN/m] in Korea. For figuring out how much water for fire-fighiting can permeate into combustibles, in this research, the permeating performance is analyzed by measuring the speed of permeating and transmission quantity released after that, by pouring solution whose surface tension is changed by adjusting concentration of surfactant BDG(Butyl Di Glycol) in column From this result, it is can be determined that transmission quantity becomes less and wet area goes wider as surface tension is lower, and it is also able to be analyzed as quantity of absorbed liquid and wet area is increased because fluid permeates into the core.