Abstract: Elaborated in the article are the process and result of the cooling test as made to the end of the SA106C seamless carbon steel pipe. Also analyzed is the effect by the cooling rate on the banded structure of the normalized carbon steel pipe,and the generation mechanism of the banded structure. The relationship between the hardness and the cooling rate is identified via the regressive analysis of the hardness and cooling rate as indicated in the CCT curve. The test result shows that when the cooling rate of the said carbon steel boiler pipe gets to 1.40~3.89 ℃/s,the structure of ferrite+pearlite structure is obtained,while the level of the banded structure is 0~3 grade,which meets the requirements as specified under applicable standard and by the customer.