The mechanism of laser paint removal is studied based on emission spectrum and composition analysis by using laser induced breakdown spectroscopy and X-ray energy spectrum technology. The electron density and electron temperature of the plasma was calculated with the LIBS spectrums with different laser parameters. The morphologies of ablated paint surface were analyzed with a scanning electron microscopy while the changes of paint composition before and after ablation were measured with an X-ray spectrometer. The results show that, the plasma electron density, temperature and ablation area gradually increase with the increasing of incident laser energy. The carbon (C) content in paint decreases from 78.25% to 67.07% after the laser irradiation, indicating the occurrence of the ablation in the process of laser paint removal. By comparing the content of titanium (Ti) elements, C element and aluminum (Al), we found that the paint ablation will be more severe at higher laser energy. This paper is important to in-depth study of laser paint removal mechanism.