An improved laser induced damage (LID) model of absorbing defects causing temperature rise in material is given. Starting with the equation of heat conduction and based on the single-defect LID model, this model gives the absorption cross section of inclusions by Mie theory. The effective interaction distance of defects in the substrate, namely the thermal diffusion length of substrate which is determined by the thermal proerties of substrate material and inclusions, is calculated. The result shows that, considering the influence of inclusions in the substrate, the obtained LID threshold (LIDT) is closer to the result of experiment than single-defect model. Meanwhile, the result of surface LIDT is very consistent with the experimental time scale of F∝t0.5.