Research on Fortresses of Gojosun(古朝鮮) Kingdom conducted by North Korean academy circle attracts attention of South Korean academy circle in that the fortresses provide the clue of understanding on the central ruling system of Gojosun Kingdom as well as giving the foundation of struggle against the military districts of Chinese Han(漢) Dynasty in Korea. Having noted this aspect, North Korean academy circle actively promoted excavation research for the fortresses of Gojosun Kingdom near the Deadong River(大同江). The representative fortresses excavated there were Bonghwa -ri Earthen Fortress(烽火里 土城), Hwangdaesung Fortress(黃垈城), Jitap-ri Earthen Fortress(智塔里 土城), Sunghyun-ri Earthen Fortress(城峴里 土城), Chongam-dong Earthen Fortress(淸岩洞 土城), and Pyungyangsung Fortress(平壤城). Among the fortresses near Pyongyang(平壤) City, Hwangdaesung Fortress is assumed to have been built in the time of Dangun Josun(檀君朝鮮), based on absolute dating and surrounding relics. In Hwangdaesung Fortress, two Dolmen and one stone-coffin tomb were found. The Dolmen found on the upper fortress wall was suspected to have been built after the fortress was abolished. It belongs to Oduk-ri type(五德里刑). Among the Oduk-ri type Dolmen, the absolute dates of the Dolmen found in Gubin-ri(九賓里), Gangdong-gun(江東郡) and the Number 4 Dolmen of Yonggok-ri(龍谷里), Sangwon-gun(祥原郡) were 4,990±444B.P and 4,539±167B.P respectively, through ESP. The skull found in a stone-coffin in the fortress was proved to be 4,795±215B.P. Based on the facts, it is suspected that the fortress wall of Hwangdaesung was built about 5000 years ago. The upper fortress walls of Jitap-ri Earthen Fortress, Sunghyun-ri Earthen Fortress belong to Hoojosun Times. The upper fortress walls of Jitap-ri Earthen Fortress were built by piling up soils, pebbles, and sands alternatively. Such method had been used till the middle age and is the evidence that Jitap-ri Earthen Fortress was built in theend of ancient times. Other fortresses that are assumed to have been built in the late of Gojosun times were Woonsung-ri Earthen Fortress(雲城里 土城), Chongsan-ri Earthen Fortress(靑山里 土城), Goyoen-ri Earthen Fortress(高淵里 土城), Nakrang Earthen Fortress(樂浪 土城), and Sorari Earthen Fortress(所羅里 土城). If the re-excavation project is promoted for them, the size of the fortress walls and construction times can be identified. As such, North Korean academy circle identified that Hwangdaesung, Chongam-dong Earthen Fortress, Jitap-ri Earthen Fortress, and Sunghyun-ri Earthen Fortress had been built in Dangun Josun Times. They suspected that Nakrang Earthen Fortress, upper fortress walls of Jitap-ri Earthen Fortress and Sunghyun-ri Earthen Fortress, Chongsan-ri Earthen Fortress, Woonsung-ri Earthen Fortress, and Goyoen-ri Earthen Fortress had been built in the Hoojosun(後朝鮮) Times. Among them, Chongam-dong Earthen Fortress was suspected to be that of Wanggeomsung(王儉城), which was the castle of the Capital of Gojosun, since it was found to have been used in the whole period of Gojosun Kingdom since it was built in Dangun Josun Times. Along the fact, the critical relic for Dangun Times was spiral type earthen china chips, which were found in Sunghyun-ri Earthen Fortress and Jitap-ri Earthen Fortress. It was connected with the characteristics of Dangun Josun times. The researches tend to newly recognize the culture of Gojosun Times since the excavation of the tomb of Dangun.