The need for smart city is emerging all over the world to solve these urban problems such as urban resource and infrastructure shortage, traffic congestion, energy problems and to preemptively respond to the fourth industrial revolution. The analysis that the security of smart city technology is dangerous is dominant all over the world. In this paper, we analyze the technology, security threats and responses of smart city, which are the main security issues of smart city, limited to smart grid, smart building, and smart traffic. In the future, the analysis of various technologies of smart city construction and the research on cyber security are actively progressing, and this paper is expected to be the beginning of the solution plan.