Abstract: The structure and optimization of tourism industry is a relative concept and dynamic process, which changes with the changes of tourism market and technology environment, tourism industry development stage and tourism economic growth. The existing research results based on the rationalization and optimization of industrial structure are too numerous to enumerate. However, the research results involving the internal evolution mechanism and regularity of the tourism industry system are still in the pre-paradigm stage, and it is rare to explore the elements of the tourism industry system and their interaction mechanism from the perspective of system science and evolutionary economics. The research idea of this paper is based on the logical thinking of induction and deduction. Firstly, the tourism industry is regarded as a complex evolution system, and the basic connotation and characteristics of its evolution are examined from a dynamic and unbalanced perspective. Secondly, it summarizes and deduces the essence, characteristics and mechanism of the evolution of tourism industry system based on the scientific research paradigm 'three theories’. Finally, based on the logical reasoning of the coupling relationship between the elements of the tourism industry system, the future research approach is explored and the conceptual model of the evolution cycle of the tourism industry system is constructed in order to promote the theoretical research on the evolution of the tourism industry structure.

Key words: tourism industry system, research paradigm, periodic evolution model, non-equilibrium