Abstract: Charged particle radiation will bring about changes of the refractive index and the extinction coefficient of the thermal control coating. The dose-depth distribution of charged particles in the thermal control coating is first discussed, then a relationship between the dose-depth and the refractive index and the extinction coefficient of materials is proposed based on the concept of the graded index, and based on that relationship, the optical property change of the thermal control coating is obtained. At last, the applications of this theoretical model are discussed.