The mid-to-late 14th century was a period of upheaval marked by dynastic changes in Korean and China. The complex international relations of the Yuan(元)-Ming(明) transition, as well as the Goryeo(高麗)-Joseon(朝鮮) transition, still require extensive research despite their historical importance. This paper examines Nahachu(納哈出), who held a significant position between Goryeo, the Ming, and the Northern Yuan(北元), and who had a substantial impact on Korea-China relations during this period. Nahachu occupied Liaodong(遼東), situated between the Ming, the Northern Yuan, and Goryeo, influencing all three powers. He posed a threat to the Ming frontier while harboring hopes for the Northern Yuan's restoration. Following Nahachu's raid on Niujiazhuang(牛家莊), the Emperor Hongwu(洪武帝) suspected collusion between Goryeo, the Northern Yuan, and Nahachu, which strained relations between Goryeo and the Ming. The Emperor Hongwu, through extensive preparation, eventually defeated Nahachu. Seizing Liaodong from Nahachu, the Emperor Hongwu established it as a forward base for further campaigns against the Northern Yuan, rapidly setting up military garrisons : Weisuo(衛所) in the region. One such garrison, Tielingwei(鐵嶺 衛), marked the signal for the collapse of Goryeo and the founding of the Joseon. Subsequent events, including Goryeo's Liaodong Conquest, Lee Seong-gye(李成桂)'s Wihwado Retreat(威化島回軍), and the establishment of the Joseon Dynasty, represent crucial turning points in Korean history. Behind these events, Nahachu's occupation of Liaodong played a pivotal role. This paper reexamines Korea-China relations during this era by analyzing Nahachu's conflict with the Ming, his relationship with Goryeo, and the Ming's occupation of Liaodong following Nahachu's fall.