Aiming at the problems of poor cutting quality and low tool life, the preparation method and cutting performance of CVD coated tools were studied. Firstly, diamond coated tools were prepared by CVD based on cemented carbide tools, and the surface morphology of the coatings was analyzed. Then, cutting experiments of aluminum alloy were carried out under different conditions to analyze the influence of diamond coating on cutting force, cutting temperature and workpiece surface roughness. Finally, through the analysis of tool wear mechanism, the effect of coating on tool life was discussed. The results show that the coating tool can reduce the cutting force and cutting temperature, greatly improve the cutting performance of the tool and the surface quality of the workpiece, and effectively improve the service life of the tool.