Based on corporate behavioral finance theory and principal-agent theory, this paper studies the impact of language tone and inefficient investment on earning management. Using the data of listed company from 2010 to 2016, this paper finds that the optimism of language tone has a positive influence on the upward earning management; the pessimism of language tone has a positive influence on the downward earning management. Further study reveals that when company facing inefficient investment, the impact of language tone on earning management is stronger. The results of this study show that language tone, as a strategic disclosure method, deepens the agency conflict between major shareholders and normal shareholders, as well as shareholders and the managers.