In this paper, we gave the definition of truth degree based on the interval interpretation of first-order fuzzy predicate logic ( or first-order fuzzy language) formulas by introducing the new ( concept) of evaluation on variable set, and discuss its a series of properties. 通过引进一阶模糊语言变元集赋值的新概念,给出了一阶模糊谓词逻辑(或一阶模糊语言)公式的区间解释真度的定义,并讨论了它们的一系列性质。