Based on the thermodynamic theory of the optical thin-film components, the thermal analysis model of thin-film components irradiated continuously by a high-power laser is established and the processes of the melting damage and the thermal stress damage induced by different kinds of surface impurities are analyzed. The statistic number of impurities inducing thermal damages on thin-film components with different sizes and different surface cleanliness levels is shown and the total thermal damage area of thin-film components induced by impurities is analyzed quantitatively. The exposure time when the thermal damage area of thin-film components exceeds 3% of the total area is calculated as well. The research results show that, under the high-power laser continuous irradiation, the melting damage and the thermal stress damage on thin-film components can be induced by impurities with sizes within a certain range. The damage way is closely related to the impurity type. The larger the aperture and the higher the cleanliness level of thin-film components, the larger the number of impurities with sizes within a certain range where the thermal damages on thin-film components can be induced. Furthermore, the damage point area of the thermal stress damage induced by a single impurity is larger than that of the melting damage.