In this paper, a method for measuring carbonation depth of cracked samples was introduced, and experiments have been carried out to determine the extent of carbonation through a crack. Comparison of the carbonation in sound concrete and in cracked concrete has been suggested. The experiment conducted to demonstrate that crack will accelerate the carbonation of concrete, and increasing crack width allows more penetration of the carbonation reaction for three kinds of penetration mentioned in the paper. Carbonation depth penetration into the sample from exposed face increase rapidly, when the crack width increases from 0 to 0.1 mm. Carbonation degree of the cracked sample is greater than that of the sound sample at the same site according to the results of calcium carbonate contents.