Position estimation based on scan matching is a type of popular approaches for mobile robat localization in indoor office-like environments. Globai scan matching and local scan mat ching are two basic position estimation problems. Global scan matching is subject to global localization for mobile robat and local scon matching is used to deal with tracking mobile robot position over time. Global localizution based on scon maiching is represented in this paper. A global map is built to represent whole environment feature and a local map is built to represent current range scan, Global map and local map consist of a lot of tine segments. Compltte line segment that represents a complete environment object is singled out and used to match between local map and giobal map. Line segments are sorted counterclockwise in two maps.This type of ardinal map improves the searching efficiency of matching and loculization algorithm is limesaving. In addition, matching between current range scan and globul map is hased on relative position relationships of line segments in local and glohal map. Glohal localization based on relative psition relationship Avoids frequent coordinates transformation and lowers computational cost. All these techniques have been implemented on our mobile robot ATRVII equipped with 2D laser range scanner SICK.