Based on analysis of operating mechanism of smart Substation Supervision and Control System (SSCS), Dynamic Bayesian Network (DBN) is introduced to evaluate the reliability of SSCS. First, the function of SSCS is divided to three types and the corresponding functional Reliability Block Diagrams (RBD) are established. Secondly, the DBN model and its solution of SSCS are implemented based on the functional RBD. Finally, a study case is presented to demonstrate the effectiveness of the proposed method. The results show that dynamic characteristics of SSCS could be well described by DBN and hence provide reference for the system configuration optimization and fault diagnosis. This work is supported by National Natural Science Foundation of China (No. 51877084), Natural Science Foundation of Hebei Province (No. E2018502063), National Key Research and Development Program of China (No. 2016YFB0900203), and Fundamental Research Funds for the Central Universities (No. 2017MS096).