Abstract: Under the three environments,normal temperature,heat and illumination,we test the light reflection spectra of the co-doped SnO₂ thin films which used the Sol-Gel method on the glass substrate to prepare Cu_TiO_2SnO₂ and Fe_TiO_2SnO₂ thin films,in ethanol,acetone to study the properties of the film to return.Research and analysis shows that the return properties of the co-doped SnO₂ thin films is not deal at room temperature environment.After 100℃ heat for 3 minutes and infrared light for 10 minutes,the return characteristic is good.