Abstract: The cloud security evolved from cloud computing has become a research hotspot in network security field, and the survivability of cloud security is particularly important. The current research status of survivability is analyzed firstly. Then the definition of cognitive survivability based on cognitive computing is proposed, and the ability of cognitive survivability is discussed. Finally, the cognitive survival model based on semi-Markov performance evaluation process algebra (SM-PEPA) is formalized and the solution of the quantitative assessment is described. The simulation experiment uses the cognitive survival index as evaluation parameters, such as survival threats, the ability to resist attacks and the richness of strategies. The proposed model is validated by solving the first passage time probability density function.