From the syntactical point of view

the concept of the syntactic truth degree of formulas is proposed in two-valued propositional logic system.Two equivalent depiction theorems about syntactic truth degree are introduced.Examples of syntactic truth degree illustrate that the original truth degree from semantics is a special syntactic truth degree.It is pointed out that the similarity degree and pseudo-metric induced by syntactic truth degree possess respectively the basic properties of similarity degree and pseudo-metric from semantics.The concept of τ -consistent theory is given.Then the intrinsic relation between τ -consistent and consistent theory is pointed out.