Abstract: Inhomogeneous chemical vapor deposition (CVD) diamond thick films are flatted by a Nd:YAG laser cutting machine with axial offset-focus. The influences of laser voltage, laser frequency and focus position on the diameter and depth of scanning spot are researched respectively. In addition, the influence of scanning step on leveling result, which is characterized by a scanning electron microscope(SEM), a roughmeter and a optical microscope, is studied. The results show that the increase of laser voltage or focus offset contributes to the increase of depth of scanning spot, and the width of scanning groove will increase with the increase of laser voltage. The roughness of the CVD diamond films is reduced significantly after a flatting process, and the graphite on the surface of the diamond film due to laser processing is efficiently removed by etching of hydrogen plasma.