Abstract: The surface reflectivity of Kevlar/epoxy doesn't change when there are no chemical and physical changes of the composite reinforcced by polyaryl amide fibers irradiated by laser beam.However it will change.The ablation threshold of the material can be obtained by monitoring its surface reflectivity changes using integrated spheres and photodiode system.This method can trace the increase of the laser power to get the ablation threshold of the material.This paper has proved the feasibility of this method by measuring the threshold of the composite reinforced by polyaryl amide fibers irradiated by laser beam with a wavelength of 1.06μm.