I. Introduction The three old theories of system theory, cybernetics and information theory are three branches of the system theory which was founded and developed rapidly in the 1940s. Although they only have a history of half a century, they are already the most respected elders in the field of systems science, collectively known as the "Lao San Lun". People took the initials of the English names of these three theories. Call it SCI theory. Dissipative structure theory, synergetic theory and catastrophe theory are branches of the three systems theories that have been established and developed rapidly since 1970s. Although their time is not long, they have become middle-aged members in the field of system science, so they are collectively called "new three theories" Also known as DSC theory. Two. Overview of "Old Three Theories" and "New Three Theories" 1. The founder of system theory, cybernetics and information theory is Austrian biologist Beta Langfield. System theory requires that things should be studied as a whole or system, and the structure and behavior of the system should be described and determined by mathematical models. The so-called system is an organic whole with specific functions, which consists of several interacting and interdependent components. The system itself is a part of the larger system to which it belongs. Bertrand Fei clearly put forward the system view, dynamic view and hierarchical view, pointing out that the role of complex things is far greater than the simple addition of all links in a causal chain, all life is in active motion, organisms can maintain dynamic stability as a system, and the system is completely open to the environment. Get the result of material, information and energy exchange. System theory emphasizes the interdependence, mutual influence and mutual restriction between whole and part, part and part, system itself and external environment. It has three basic characteristics: purpose, dynamics and order. Cybernetics was founded by the famous American mathematician Weiner and his collaborators to consciously adapt to the development trend of mutual infiltration and integration of different categories in modern science and technology. It got rid of the shackles of Newton's classical mechanics and Laplace's mechanical determinism. The possibility of using new statistical theory to study the motion state, behavior pattern and changing trend of the system. Cybernetics is a technical science that studies the state, function, behavior and changing trend of the system, controls the stability of the system, reveals the control laws of different systems, and makes the system run according to the predetermined goal. Information theory was founded by American mathematician Shannon, and it used the methods of probability theory and mathematical statistics. The science that studies how to acquire, process, process, transmit and control system information quantitatively. Information refers to the new content and new knowledge contained in information. Used to reduce and eliminate the uncertainty of people's understanding of things. Information is the basis for all systems to maintain a certain structure and realize functions. Narrow sense information theory is a communication theory that studies the same information transmission law that exists universally in communication systems and how to improve the effectiveness and reliability of various information transmission systems. Generalized information theory is understood as a theory that uses the viewpoint of narrow information theory to study all problems. According to information theory, the system is realized through the acquisition, transmission, processing and processing of information.