Abstract: By solving a thermal conduction equation with Green’s function method, a theoretical model is developed to describe the three-dimensional temperature distribution of a highly reflective optical coating sample with a finite radial size irradiated by a continuous-wave laser beam. The radial boundary conditions and heat losses from the sample to the environment are both considered in this model. To verify the theoretical model, temperature distributions are numerically calculated under different pump-beam profiles and beam radii and the results are in good agreement with those of the finite-element method. Furthermore, the influence of different thermal loss coefficients on the temperature distributions of the sample irradiated by laser beams is discussed.