Diamond is an excellent material in terms of hardness, thermal conductivity and chemical stability. In order to broaden its application area, the interaction mechanism of CVD diamond processed by femtosecond laser is analyzed based on laser micromachining technology. Through the threshold theory, the ablation threshold of CVD diamond is calculated. At the same time, the graphitization phase transition occurred in the diamond. The internal elements before and after the ablation of diamond by femtosecond laser are characterized by X-ray energy spectrum analysis. The changes of element content and bonding form are analyzed, and the relevant graphitization mechanism is revealed.