The need to implement wastewater reuse in Beijing is discussed. Based on the investigation of the built wastewater reuse projects in Beijing, the differences between small wastewater reuse system and large systems were analyzed according to the technical, economical and social issues. The advantages and disadvantages of the small system and the large system were then given. In wastewater reuse planning in Beijing urban region, the large system was adopted. The rations of reclaimed water for difference land use type, including industrial reuse, municipal reuse, grass irrigation, and scenes water reuse were determined. Then according to the land use information in every block in central Beijing, using GIS techniques, the amounts of the reclaimed water needed in every block were calculated, and the main pipe system of reclaimed water was planned.