Abstract: Medium logic is a kind of logic system which differentiates contradiction from opposition，and affirms that there exists medium between some opposite information.Based on medium predicate Logic，the paper represents fuzzy knowledge，modifies and-or graph with reason，regards every predication expression as state node to convert logic formulary into searching space.Then the heuristic function of traditional searching method of and-or graph is modified in order to treat fuzzy reasoning problem as problem of searching for the most reliable goal node.It also gives a kind of treatment method to manage negative information.

Key words: medium logic, fuzzy knowledge representation, state space, and-or graph, heuristic function, negative information

摘要： 中介逻辑是一种区分矛盾否定与对立否定、肯定一些对立知识间存在中介对象的逻辑系统。基于中介谓词逻辑描述模糊知识，合理修改与或图，将每一谓词表达式视为状态结点，把逻辑规则集合表示为状态搜索空间。在传统与或图搜索算法的基础上，修改启发函数，将模糊知识的推理问题转化为状态空间中的搜索问题，并给出了一种否定信息的处理方法。

关键词: 中介逻辑, 模糊知识表示, 状态空间, 与或图, 启发函数, 否定信息