Robots are increasingly entering people’s daily life and are receiving more and more attention in China and abroad. One of the important characteristics of robotic systems is security, and enhancing the security of robotic systems can protect robots from malicious attackers. The security of robot operating system (ROS) is an important part of the security of robotic systems. Although researchers have done a lot of research work on the security of ROSs in recent years, unfortunately, security has not received enough attention yet. In order to draw more attention to the security of robotic systems and help people quickly understand the security solutions of the current mainstream ROS, this study systematically investigates and summarizes the security of ROSs. On the one hand, this study analyzes the security features of ROSs and discusses the known security problems in ROSs. On the other hand, this study categorizes and summarizes the research related to the security of ROSs in recent years and compares the security solutions of ROSs in terms of confidentiality, integrity, and availability. Finally, this study prospects the future of security research on ROS.