Wedge splitting tests of the concrete specimens after exposure to high temperature were conducted. Adopting three bilinear softening curves at room temperature and taking account of the quantitative relationship among unstable fracture toughness KIC,un,T, initial fracture toughness KIC,ini,T and cohesive fracture toughness KIC,c,T from the double K fracture model, the relationship of these three parameters for the concrete after exposure to high temperature was investigated. There are two cases of calculation of cohesive fracture toughness KIC,c,T, and the similar values of KIC,c,T are obtained from the calculation using different softening curves. The calculated unstable fracture toughness KIC,un,Tbased on the three softening curves has a good coincidence with the experimental value, which shows that the softening curves could well reflect the real fracture feature of the concrete after exposure to high temperature and the adaptability of application of double K fracture model to the concrete after exposure to high temperature is proved.