：With the high integration of informatization and industrialization, the degree of intelligence and automation of the secondary system of substations has been continuously enhanced. While enjoying the convenience, we also need to face the challenges and threats brought by the Internet. In view of the confidentiality, integrity and other security threats that the secondary system applications or tools may face during the calculation and transmission process, the enhanced security terminal protection technology based on the USB interface has become a research hotspot. Although the traditional enhanced security terminal equipment is easy to produce, the algorithms in it have been specified by the manufacturer and downloaded to the corresponding equipment. Considering that the security requirements of different scenarios are quite different, and different users have multi-level security requirements, the AVR microcontroller is programmed through the Arduino IDE platform, and an enhanced security terminal equipment with general algorithms is designed and implemented, which not only realizes functions such as identity authentication and content encryption, but also meets the personalized needs of users' independent choices and improves the security and controllability of the entire secondary system. After the test, the usability and robustness of the terminal are preliminarily proved.