High power laser is essential for optical manipulation and fabrication. When the laser travels through optics and to the target finally, irreversible damage on the dielectric coating is always accompanied without knowing the law and principle of laser induced damage. Here, an experimental study of laser induced damage threshold (LIDT) F-th of the dielectric coating under different pulse duration t is implemented. We observe that the temporal scaling law of square pulse for highreflectivity (HR) coating and anti-reflectivity (AR) coating are F-th = 9.53t(0.47) and F-th = 6.43t(0.28) at 1064 nm,respectively. Moreover, the intrinsic LIDT of HR coating is 62.7 J/cm(2) where the coating is just 100% damaged by gradually increasing the fluence densities of a 5ns-duration pulse, which is much higher than the actual LIDT of 18.6 J/cm(2). Thus, a more robust and reliable high power laser system will be a reality, even working at very high fluence, if measures are taken to improve the actual LIDT to a considerable level near the intrinsic value. (C) 2017 Elsevier B.V. All rights reserved.