The life span of external insulation building which is related to the speed of concrete's neutralization has connection with the air permeability of external insulation method. This study generally measures the air permeability of external insulation method, and examines the restraint effect of neutralization in external insulation method from the accelerating test of concrete's neutralization. In addition, it described the relations between the air permeability of external insulation method and the restraint effect of neutralization.