Abstract: This paper reviews the concept of discretization lattice composed by discretization schemes，proposes the concept of ordered partition of universe U，and discusses a special kind of discretization schemes named closed discretization schemes.We give a closed discretization scheme acquisition algorithm （CDA） for an ordered partition of universe U，analyze the relationship between closed discretization schemes and ordered partitions，and draw the conclusion that under the function f from discretization lattice to partition lattice，closed discretization schemes hold the union and intersection operations.

Key words: closed discretization schemes, discretization lattice, ordered partition, rough set

摘要： 提出对象域U的有序划分概念，讨论一种特殊的离散化方案（闭离散化方案）。给出对象域U的有序划分对应的闭离散化方案获取算法CDA，分析闭离散化方案与对象域U的有序划分之间的关系，证明了闭离散化方案在离散格到划分格的映射f下能保持交并运算。

关键词: 闭离散化方案, 离散格, 有序划分, 粗集