The old electric transmission tunnel over thirty years old in northern Seoul is operated with Ttukdo substation as its starting point and 41km-length since March, 1980, and the trend is an icrease in embedded electric power structures over thirty years old beyond sixty kilometers. If the corrosion occur in reinforced concrete structures, it is considered as the important factor among deterioration factors .By examing the seventy-two cases of concrete carbonation and covering depth in order to analyze the concrete carbonation of electric power structures over thirth years old in Gangbuk-gu, this paper atempts to analyze carbonation coefficient, remaning service life, and concrete carbonation of old embedded electric power structures for reference to predict the concrete carbonation progress.