关键词: 相变，SAT问题，参数问题，backbone集合

Abstract: Phase transition exists in many problems of Artificial Intelligence. Phase transition is with a little change to the parameter there is a sharp transition to the system. There is a great relationship between phase transition and the structure of problem, this paper made more comprehensive introduction about the developing, related concepts of phase transition and the relationship between phase transition and the structure of problem. Moreover, summarized some unresolved questions and given the summary and outlook of research on phase transition.

Key words: Phase transition, Propositional satisfiability problem, Parameter problem, Backbone set