Since 1996, the president of Taiwan's implementation of universal suffrage since 2010 in 14 years, There have been twice to replace the regime of peace, Taiwan's policy toward mainland China in the political division of the two major political parties - the KMT and DDP and also so the identity of the ruling and opposition parties quickly converted twice. Taiwan's political environment has undergone an unprecedented rapid changes. This article by David Easton's system theory as a general theory and approaches, Looks forward to further establishing a political party as the core of the local theory, Analysis of Taiwan's political parties since 1996 in the "internal and external environment ¡÷ demand and input ¡÷ feedback and output ¡÷ re-enter to the internal and external environment" and what role in the political process? As well as how the policies of mainland China affected? ¡@This article has found, political parties in the system theory are not only pressure groups for Political authority, And active in the political system's internal, external and boundary, And can be further repression of political authority, the completion of its own expectations of mainland policy. Political parties, both ruling party or opposition parties or unified government or divided government, the political parties can control congress, congressional paralysis, cooperation with other political system, increased support by social mobilization, the creation of political controversy and use other methods to pressure on the political authority. Finally, this article believes that with the cooperation of the KMT and the China Communist Party platform, the KMT has similar status of political authority in Taiwan's policy toward mainland China.