In this paper, we propose the multi-living agent (MLA) concept based on the of analysis the characteristics of complex information systems, especially those systems that require multi-functional operations under strict restraint strong countermeasures (SRSC) environment. First, we investigate the representation of the livelihood of the system under the SRSC conditions, and obtain the basic dynamical presentation of the MLA from the profile of the system’s function. Next, we propose the concept of the living self-organization based on the self-organization profile of the system, and derive a Two-Set model of the living self-organization mechanism. Further, based on the above results, we present a basic construction model of MLA-based information systems in the field of information security and countermeasures. A three-level negotiation-coordination mechanism is also derived. Finally, we present two practical examples to show how to use the MLA concept to analyze and study real complex information systems. In our opinion, the proposal of the MLA will bridge the gap between the research of the application and the basic application level of science. It provides the principle research methods and the supporting theories for the construction and analysis of complex information systems in the information security and countermeasures field. In this paper, we propose the multi-living agent (MLA) concept based on the of analysis of characteristics of complex information systems, especially those systems that require multi-functional operations under strict restraint strong countermeasures (SRSC) environment. First, we investigate the representation of the livelihood of the system under the SRSC conditions, and obtain the basic dynamical presentation of the MLA from the profile of the system’s function. Next, we propose the concept of the living self-organization based on the self-organization profile of the system, and derive a Two-Set model of the living self-organization mechanism. Further, based on the above results, we present a basic construction model of MLA-based information systems in the field of information security and countermeasures. A three- level, negotiation-coordination mechanism is also derived. Finally, we present two practical examples to show how to use the the MLA concept to analyze and study real complex i nformation systems. In our opinion, the proposal of the MLA will bridge the gap between the research of the application and the basic application level of science. It provides the principle research methods and the supporting theories for the construction and analysis of complex information systems in the information security and countermeasures field.