Abstract: In this paper，magnifying or reducing principle and magnifying or reducing resolution principle of lattice-valued propositional logic L₉P（X） are given.Based on the magnifying or reducing resolution principle，an automated reasoning algorithm is given which can be used to decide if a clause set S is M－satisfiable，where M is an intermediate element of L₉，and its soundness and completeness are proved.

Key words: intermediate element, lattice-valued propositional logic, automated reasoning based on resolution, magnifying or reducing resolution principle, automated reasoning algorithm

摘要： 给出了格值命题逻辑系统L₉P（X）上的放缩原理和放缩归结原理，基于放缩归结原理，给出了一种判断L₉P（X）上子句集S为M－可满足的自动推理算法（这里M为L₉上的中界元），并证明了其可靠性和完备性。

关键词: 中界元, 格值命题逻辑系统, 归结自动推理, 放缩归结原理, 自动推理算法