This field research on Dongmoushan area in Dunhua and Xigucheng area in Helong,which are two former capital regions in the early Bohai period (698-756),focuses on exploring locational characteristics and spatial relationship among the scattered relics in the study areas.In order to identify locational characteristics of the capital regions,such elements as physical landscape,climate condition,land use,and transportation routes are reviewed.Dunhua,located at the altitude of 150-200 meters higher than Helong,tends to be disadvantaged in terms of climate and agricultural activities.At the same time,in the respect of the total arable land developed along fluvial plain of the Helong river,the Helong maintains favour location for agricultural potentiality,comparing with Dunhua location where volcanic lava filled in the most low land area along Mudan river.It is partially guessed that the primary geographical conditions influenced to move from the first capital in Dongmoushan to Xigucheng.Based on observation of the relic distributions,it seems that two capitals have never been formally arranged by the ancient urban planning.The spatial distribution of Dongmoushan fortress,Aodongcheng Wall,Yongsheng site,and Liudingshan mounds suggests that the structure of early capital was formulated by favourable physical location for defence,affluent arable land along the river,and convenient transportation route rather than by a formal layout plan.The case of Xigucheng in Helong,which was the second capital,reflects that the capital wall in river plain has been constructed by planning.But the planning has not been completed.The geographical characteristics such as physically favour location for defence,severe winter climate,agricultural potentiality,and transport route,seem to have partially influenced the location of the capitals in the early Bohai period.