High performance concrete will undergo thermal-mechanical degradation or even spalling under high temperature conditions, such as fire, and the safety of concrete structures will be endangered. To prevent concrete from fire damage, the damage mechanism should be thoroughly understood. In this paper, an anisotropic damage model is presented to analyze the thermal-mechanical degradation of concrete. The vapor pressure and the moisture transport are taken into account. The damage evolution history can be traced with the temperature propagation and the degree of material degradation can be predicted through the model.