While the Chinese Civil War has mostly been explored by historians through the lens of military and diplomatic history, this thesis focuses on a trans-Pacific interaction between China and the US. In particular, it asks about what the Chinese Communist Party (CCP) and the Kuomintang (KMT) did in America and how their different approaches influenced China politics. This thesis examines the KMT and the CCP’s lobby and interactions with both the Americans and overseas Chinese in the US and argues that the CCP not only won the Chinese Civil War against the KMT in China but also won the war of convincing and attracting the Chinese people in America. KMT’s lobby not only failed to achieve its aim but deteriorated its image in the US, and its political surveillance further alienated itself from the overseas Chinese. On the contrary, though the CCP has fewer previous links with America, its popularity was largely built on the comparison with the KMT. The lobbies and exoduses altogether created the complicated trans-Pacific China politics from 1945 to 1951.