Floating reactor is a combination of reactor and ship, and the operating environment is the sea. Its security is quite different from the land reactor in terms of design basis threat, protection area division and preventive measures. The existing legal standards of large reactor is not fully applicable to floating reactor. Because floating reactor combine the characteristics of ship, security should consider the different requirements of ship at the same time. Therefore, it is necessary to carry out research work on the security of floating reactor. By studying and analyzing the security characteristics, main threats and general protection requirements of floating reactor, taking the floating reactor as an example, this paper innovatively puts forward the protection idea of five security zones, the system configuration framework and the specific configuration case of water security. It also analyzes and studies the elements of human defense of security scheme, compares the advantages and disadvantages of potential response force, and puts forwards the suggestion of response force configuration foe floating reactor. Through this study, it provides the design idea and reference scheme for the security design of floating reactor, and lays the foundation for the subsequent formulation of floating reactor security standard.