Abstract: Nuclear power plant emergency command system can provide valuable data for emergency personnel, such as the unit data, weather data, environmental radiation data. In the course of emergency response, the emergency command system provides decision support to quickly and effectively control and mitigate the consequences of the nuclear accident, to avoid and reduce the dose received by staff and the public, to protect the environment and the public. There are high performance requirements on the security of the system and the data transmission. Based on the previous project and new demand after the Fukushima incident, the security technology design of emergency system in nuclear power plant was discussed. The results show that the introduction of information security technology can effectively ensure the security of emergency systems, and enhance the capacity of nuclear power plant to deal with nuclear accidents.