Abstract: The stable carbon isotopic compositions of tree ring have been explored to study paleoclimatic variations, past atmospheric CO 2 level, and global carbon cycle. This paper analyzed the carbon isotopic ratios of two cryptomeria , collecting from West Tianmu Mountain, Zhejiang, and studied the tree ring carbon isotopic ratios evidence, for the atmospheric CO 2 concentration change after Industrial Revolution. The calculation of CO 2 construction fits well with the records. The tree ring carbon isotopic ratios well records the atmospheric carbon ratios change, which provides a good evidence for the CO 2 changes and a new means for the study on atmospheric CO 2 changes.