Based on information technology, smart government processes information data to help improve the efficiency of government operations. Information security has become the key to the transformation of government wisdom and improvement of government service efficiency and transparency. To explore the influencing factors of government information security, 27 influencing factors from 6 dimensions of personnel, facilities, information, personnel management, system, and environment were extracted. The decision-making trial and evaluation laboratory (DEMATEL)-interpretative structural modeling (ISM) composite model was used to determine the importance of each factor, the mechanism between the influencing factors was analyzed, and a smart government information security interpretation structure model was constructed. Results show that policies and regulations are the root factors affecting the information security of the smart government. The international environment is a deep-layer influencing factor on government information security. Infrastructure, moral training, and other factors are middle-layer influencing factors that are influenced by the superior factors. Psychological factors, platform construction, and others are surface-layer influencing factors that play a connecting role. Security awareness, behavior security, moral level, and others are directly influencing factors and determine the level of smart government information security. Results of this study also show the feasibility of DEMATEL-ISM model in identifying the relevant factors and analyzing their influencing mechanism on smart government information security. A novel modeling method and its analysis approach are provided for the government to improve the level of information security.