Diamond-like carbon (DLC) films have being widely applied in various domains owing to their excellent optical and mechanical properties, chemical inertness and bio-compatibility[1,2]. But it generally exhibits low a laser induced damage threshold (LIDT).As to infrared protective films, DLC films were asked to be a high laser damage threshold. So far, the real reason of laser damage is unclear. In order to understand the real reason of the laser damage, it is necessary to deeply research the relationship between optical properties and laser radiation. In this paper, optical properties post irraditing by various laser energy were inverstigated. Hydrogen-free amorphous carbon films were deposited by unbalanced magnetron sputtering with a graphite target on Si substrate in this paper. The DLC films were radiated with raster scans methods by a 1064nm and 8–10 ns laser in this work. The transmittance, refractive index, extinction coefficient and surface morphology of DLC before and after radiation were examined by fourier transform infrared spectrometer, ellipsometer and talysurf respectively. The influences were considered as function of laser energy density.The optical properties before and after laser radiation were compared. It is found that as laser fluences rise from 0 to 0.5 J/cm2, the transmittance peak reduce from 67.06% to 58.27%, the refractive index decrease from 1.88 to 1.67(λ=1200), the extinction coefficient increase from 0.07 to 0.32(λ=1200), and the surface roughness become 149.28nm in this procedλure. Especially, the reasons of change were expounded in this paper.