These days the impact of North Korea on the Northeast Asian region is quite significant. The nuclear issue of North Korea has emerged as the most important diplomatic and security challenges in Northeast Asian countries, and becomes a more sensitive issue due to the instability of the North Korean situation. In order to settle these diplomatic challenges and to maintain peace and stability in the region, it is very important to comprehensively analyze the impact of China on North Korea, considering the increasing influence of China on the region over the past decades and close relationship between China and North Korea, known as the so-called "lips and teeth relations". After being defeated in the 1895 Sino-Japanese War, China had been cut off from the Korean peninsula for more than half a century. The country was involved in Korea by sending hundreds of thousands of soldiers to the Korean War in October 1950 under East-West Cold War system which started after World War Ⅱ. In July 1961, China and North Korea signed the "Treaty of Friendship and Cooperation" and built an alliance between the two countries. Until the diplomatic ties between China and South Korea in August 1992, China and North Korea had maintained the fraternal relations in political, economic, military and social issues. Since the normalization of South Korea and China, however, the China-North Korea relationship has significantly changed, and China's influence on North Korea was doubted. How did today's North Korea-China relations change from the past alliance relations? And to what extent does China have influence on North Korea? This paper tries to analyze, based on the awareness of these issues, the impact of normalization of South Korea-China on the relationship between North Korea and China, especially the influence of China on North Korea in politics, the economy, military and other fields. At the same time, the potential impact China will have on North Korea in the future will be analyzed.