Abstract: Unmanned swarm is an important application and key technological development direction of unmanned systems. Compared to single unmanned aerial systems, unmanned swarms demonstrate significant technological advantages in terms of coverage range, operational efficiency, and ability to execute complex tasks. However, unmanned swarm still faces severe information security issues. Due to the need to operate in complex and dynamic open electromagnetic environments, there are numerous potential security threats and challenges in the collaboration, communication, authentication, and identification processes of unmanned swarms. This article aims to conduct in-depth research on the security issues of unmanned swarms, analyze potential security threats, review existing security measures, and explore emerging security solutions. It will extensively investigate and analyze key aspects of unmanned swarm security, including individual security, network security, identity security, communication security, and data security. The goal of this article is to provide support for research and applications related to unmanned swarms.