Abstract: Traditional logic is binary, and for the future, such as accidental proposition, this logic can not solve, which is different from the need to develop logic of binary logic, which is multi-valued logic, the three-valued logic is the most basic form. Today, three-valued logic theory along the different routes has been developed rapidly, its increasingly wide range of applications. Threevalued logic systems and their relationship with the classical two-valued logic of the distinction between internal and contacts show their unique ideas and construction methods.