2008年1月12日第七屆立法委員選舉結果出爐，中國國民黨贏得四分之三席次，民主進步黨則遭受重挫。這是臺灣第一次實施單一選區兩票制的選舉，此次立法委員選舉適用任務型國民大會代表複決通過的第七次修憲案。第七次修憲〈憲法增修條文〉第4條規定，立法院立法委員第七屆起改為113人，包括區域立委73人，平地及山地原住民各3人，全國不分區及僑居國民則是依政黨名單投票選舉，由獲得百分之五以上政黨選舉票之政黨依得票比率選出。早在修憲之初，各政黨即對於單一選區兩票制如何設計有過論爭，由於修憲需要立法院四分之三委員通過提案，表示該一改革乃獲得各政黨之高度共識與支援。其中國、民兩黨對於影響其存續的此一重大改革，究竟是基於何種考量予以支援，其是否預見此一選舉實施結果，則為本研究之主題。本研究將採歷史途徑，以文獻方法和訪談方法，回顧此一重大憲政改革之決策過程。

In Taiwan, the Single-Member Districts and Two Votes System first time launched in the seventh Legislators election in January 12, 2008. The Kuomingtang won majority by three-quarters of seats, despite the Democratic Progressive Party had been totally frustrated.The seventh constitutional amending in which the National Assembly of the task-based approved was a new system of the Legislators election. The Single Non-Transferable Vote under Multimember-District System had been adopted since the Legislative Yuan was founded. The fourth provision of the Seventh Amendment of the Constitution required that since the seventh Legislative Yuan, there are 113 legislators with 4 year term in the office. The electorate regulation has been amended as follows: 1. 73 legislators shall be elected from the Special Municipalities, counties and cities; 2. 3 members each shall be elected from among aborigines; 3. 34 members shall be elected from the nationwide constituency and among citizens residing abroad; 4. members to fill the seats shall be elected from the lists of political parties in the proportion to the number of votes won by each party that obtains at least five percent of the total votes.There are controversial issues involving the details of the Single-Member Districts and Two Votes System among all parties during the seventh constitutional amending. Because draft constitutional amendments must be approved by at least three fourths of the members of the Legislative Yuan at a meeting attended by at least three fourths of the total members of the Legislative Yuan, it means that the Electoral System Reform were consented and supported by all parties in the Legislative Yuan. The theme of the study is the considerations and the foresights between KMT and DPP for the constitutional reform’s impact about their individual existence. The study will review the process of the constitutional decision-making by documents and interview methods with historical approach.