With the development of new equipment and new technologies in the fields of intelligent equipment and wireless communication, there has a more complex access environment, flexible access mode and a large number of intelligent access terminals in smart grid. These new changes have increased the difficulty of information security protection in smart grid. This paper focuses on the research of IoT applications and security risk analysis for smart grids, proposes the basic architecture of IoT applications for smart grids, and addresses IoT security key technologies and risk analysis for smart grid. Through the analysis of the application and security risks of smart grid, it will provide a solid security guarantee for the safe and stable operation of smart grid.