Chinese situation is deteriorating in the period from the end of 1948 to the end of 1949, Nationalist has lost whole Manchuria and the most northern China. President Chiang resigned again under the pressure of worsen situation. Chiang's resignation means that the Nationalist is hopeless in Mainland China. Dean Acheson is facing the chaos in China, when he is appointed to be George Marshall's successor, become the U.S. Secretary of State. Cutting off the relations between U.S. and Nationalist China has been the basic route of China policy after his inauguration because he is influenced by the preconception of China in the Department of State, and China White Paper in 1949 is the embodiment of the route. Besides cutting off the relations between Nationalist, however, Acheson does not get any accomplishment in other aspects of his China Policy. Acheson is not concordant with the Congress either, because his personality and the confrontation between Republican and Democratic in the Congress. This paper will discussed that in the process of Acheson's China Policy developed, how the situation both internal and international, Acheson's personality, and his preconception of China, influence his final decision.