Abstract: In this paper, the method of proof test and failure predication for thermal tempered glasses has been established for the first time, based upon fracture mechanics and the distribution of stress in thermal tempered glass, which provids the theoretical foundation for the strength check of the window glass of spacecraft. The results of calculation examples show that the permissible loads will different in different application environment, even if the glass has passed the same test stress in prooftest. The life time of glass under the same load also depands greatly on the environmental conditions.