過去區域立委在複數選區單記不可讓渡投票制之下，有強烈的動機去建立個人選票，為了達到此一目標，有些立委強調選區服務，有些立委強調立法問政。在2005年6月將區域立委改為單一選區制，那麼，當選舉制度變革之後，立委的代表行為是否因為選制改變而有所調整？本研究以質化與量化為資料蒐集方法，聚焦在第五屆到第七屆區域立法委員（任期自2002年2月到2012年1月）。研究發現顯示：新選制下的立委較過去更強調選區服務，他們花更多的時間與資源在選區，且對選區服務的態度更為慎重，不僅作更多的選區服務，且服務的內容更為廣泛多元。然而，他們也不偏廢立法問政，只是在資源與時間有限的情況下，會用更策略性的方式來從事立法問政：他們將立法權委任行政機關，然後僅加以小幅度修改，提出一到兩個條文的提案，甚至於有時他們會去與其他立委共同提案，這種立法型態在舊制下就有，但是在新制下更被增強。最後，當立委真的在選區服務與立法問政無法兩全，而必須二者擇一時，立委仍會以選區服務為重。 Under the old SNTV electoral system, Taiwan's district legislators have an intensive motivation to pursue personal vote. To attain this goal, some legislators make more efforts on the activities of constituency service, while others make more efforts on the activities in the legislative process. In June 2005, Taiwan's electoral system for district legislators had reformed to a single member district plural system. In this article, I conducted quantitative and qualitative research methods and focus on district legislators from the Fifth to the Seventh Legislative Yuan (from February 2002 to January 2012) to explore whether legislators change their behavior because of the system reform. Research findings show: legislators under the new electoral system emphasized even more on constituency service. They spent more time and resources on constituency, and their attitudes toward constituency service were even more cautious. They not only conducted more casework, but also they conducted casework much more widely diversified. At the meantime, legislators did not ignore legislative work. Owing to the limitation of time and resources, legislators engaged in the legislative process strategically. They delegated legislative power to the administrative branch. They then modified those bills proposed by the administrative branch and proposed their own version of bills with only one or two articles. Sometimes, they might co-author the bills proposed by their colleagues to save time and resources. This legislative style had appeared under the old system. It was reinforced under the new system. Finally, if they had to make a choice between constituency service and legislative work, most legislators were inclined to the constituency service.