Party identification has long been regarded as a major factor in determining the vote decision. However, in Taiwan’s case, since the Democratic Progress Party (DPP) won the 2000 presidential election, Taiwan’s party system changed dramatically, which certainly affected the electorate’s party identification. Hence, this study would like to focus on the transition of Taiwanese voters’ party identification and the relationship between party identification and vote decision. The study found that the social structures of Taiwanese political parties are different in terms of age, education level, living area, race, and standpoint of cross-straits relations. As for the transition of party identification, the DPP has a stable block of party identifier (around 30%) and the number of Kuomintang’s party identifier (KMT) is growing continually. Furthermore, party identification does affect the vote decision. The voter with a certain party identification tends to vote for the candidate nominated by the party he/she supports.