With a view to attaining the sharability and consistency of map information under distributed environment, we propose a Multi-level/Multi-theme map information model to maintain maps in consistency with original source datasets under distributed environment. However, the distributed management of spatial datasets results in a complex maintenance processing, especially when the modification refers to several datasets. To solve this problem effectually, in this paper we propose an index structure, MOR-tree (Multi-levels of Object-Relation tree), for organizing integrated maintenance procedure. MOR-tree is an extension of R-tree for indexing spatial objects of multi-levels in one hierarchy and records relations among objects at different levels. The performance of MOR-tree is also evaluated with a prototype system in this paper.