本文目的在於探討選舉制度的改變對國會議員競選政見，和其實踐政見之立法表現的影響。本文提出兩個假設：第一，單一選區相對多數制（SMP）下產生的國會議員，會比比例代表制（PR）下的更傾向提出地方性的政見，但不會增加社福政見；第二，SMP制下選出的議員，也會比PR制下的更努力將政見落實於立法表現的各項行為中。本研究以臺灣立法院為對象，進行準實驗設計比較。立法院第六屆（2005－2008）及第七屆（2008－2012）所使用的選舉方式，分別是以接近PR制的SNTV制為主的混合制，以及以SMP為主的兩票並立混合制。透過登錄第六屆與第七屆區域立法委員的公報政見及立法表現相關資料，探討比較選舉制度變遷對國會議員競選政見和其實踐政見之立法表現的影響。本文的發現基本肯定兩項假設，也就是SMP確實促使區域立委提出較多與地方選區有關的政見，但不增加社福政見；也驅動區域立委以較正式、可被觀察紀錄的立法行為，如法律提案及臨時提案，來實踐其政見。本文針對這些發現，更進一步探討以SMP和PR兩種制度所產生之代表的回應性和課責性，以及對社福政策之影響，來反思目前民主憲政設計較推崇PR制的趨勢。 This paper explores the impact of alterations to electoral systems on legislator campaign promises and to what extent legislators keep these promises in later legislative performance. We advance 2 hypotheses: 1. Legislators elected in single member plurality (SMP) system have a greater tendency to propose locally oriented campaign promises than those elected through proportional representation (PR), but will not be more likely to advance social welfare campaign promises; 2. Legislators chosen through SMP will put forth greater effort to actualize campaign promises in various legislative activities.This research performs a quasi-experimental comparison on Taiwan's Legislative Yuan. The 6th Legislative Yuan (2005-2008) utilized a single non-transferable vote system (SNTV), which was a hybrid system similar to PR, while the 7th Legislative Yuan elections were primarily an SMP hybrid two ballot system. We record data for the campaign promises district legislative candidates officially announced during the 6th and 7th term elections to explore the influence of electoral system alterations on national legislators' campaign promises and legislative activities aimed at realizing these promises.Our study essentially verifies the two hypotheses. SMP leads legislators to advance larger numbers of locally oriented campaign promises, while there is no difference between SMP and PR with respect to social welfare campaign promises. SMP system also spurs district legislators to utilize official and observable legislative activities, such as legislative proposals and interim proposals, in adhering to campaign promises. With respect to these findings, we further explore responsiveness and accountability in the SMP and PR systems, as well as its impact on social welfare policy, in order to further reflect on the present trend toward greater respect for PR system in democratic constitutional design.