We have examined the characteristics and distortions of China's researches on Manchuria history of Ming Dynasty and its countermeasures. Liaodong was located east of the Great Wall and Shanhaiguan. Based on its geographical position, Liaodong debauchment by Ming Dynasty was made possible through human and material support from Shandong. Through the victory from Northern Yuan, Ming Dynasty was able to connect Liaodong and Shanhaiguan and began to strengthen a defensive structure of Liaodong. Rooted in Liaodongdusi, a local defensive headquarter, Ming Dynasty strengthened its defensive structure. However, Ming's attempts to influence Mongol and Jurchens areas were unsuccessful. Despite Liaodong was based on Wei-suo system, most of them had to be depended on Shandong. Another factor which inhibited Liaodongdusi to expand was the growths in power of Mongol and Jurchens. Despite Ming's attempts to take over Mongol and Jurchens, most of times, they were unable to succeed. Tieling-wei and Sanwan-wei, which initially planned to be established near Ablok(Yalu) and Duman(Tumen) Rivers, bad been absorbed by Liaodongdusi Moreover, a conflict (concerning Jurchens near Duman(Tumen) River) between Chosun and Ming could not be resolved due to diplomatic failures of Ming Dynasty. Consequently those Jurchens were incorporated into Chosun; Ming Dynasty's plan to include Jurchens area into their territory thus failed. During Yongle years, Yongle's 5 direct rule invasions to Mongol seemed effective and by establishing Nuergandusi and more than 180 of Jurchens Wei-suo, it seemed to temporarily expand Liadongdusi's power of influence over to Jilin and Heilong-River. However, Nuergandusi, losing its initial function, was eventually absorbed by Liadongdusi, and Jurchens newly surfaced as an intimidating figure to Ming Dynasty. Nuergandusi had to be supported by Liadongdusi in terms of human and material resources, and was merely a temporal military organization, not having judicial and administrative authority. During Xuan-de and Zheng-tong years Nuergandusi lost its functions and completely incorporated into Liadongdusi; no continuing military activities, Nuergan area was out of the picture. Not only a limitation in outer expansion, Liadong policy of Ming dynasty was in danger as a whole. Crops from farms, cultivated by stationary soldiers, decreased due to breakaways of Wei¬suo soldiers, and runaways, riots of population, thus, impairing its defensive powers. Confronting these various crises, Ming Dynasty had to change its defensive line to barricades and could only contract a region to its initial form. A contraction of the region was the only choice Ming could choose. Liadong barricade was classified into 3 areas, Liaoxi(遼西), Liaohetao(遼河套), and Liadong barricades. Barricades, a last choice for Ming Dynasty, couldn't perform a role of solid defensive line. Due to the failure of Wei-suo system, they were unable to allocate human resources over the long lines of barricade, consequently, not functioning properly. A contracted Liadong barricade not only a defensive line of Liadongdusi but also a country boundary. Thus, Jurchens region, a region out of barricade line, was out of their influence. This contradicts a current China's claim that Jurchens were part of Ming Dynasty and Yalu and Tumenjiang rivers were boundaries between Chosun and Ming. Moreover, historical documents considered that Jurchens were not part of Ming Dynasty and recognized Jurchens region as wai-yi (外夷) region. In later of Ming Dynasty, due to external threats from Mongol and Jurchens, and internal maximization in contradiction, there were a great decrease in production, shortage of battle horses, and riots. Liadong, located Far East, was an important military base during Liadong times. Liadongdusi was a central organization which managed Liadong and defended north. However, as suggested above, while Liadongdusi expanded to the farthest during Yong-le years, debouchments to Jurchens failed due to growth of other competitive patties. Thereafter Ming Dynasty formed a defensive line focusedon barricades which also was boundary between countries. Even Liadong barricades fell in later years of Ming Dynasty by the Later Jin Dynasty.