香港的選舉制度在幾十年內經歷顯著變化，其中立法會地區直選制度從最初的雙議席雙票制改為單議席單票制，最終確定為比例代表制。本研究旨在分析選舉制度變革的政治後果，特別是對香港政黨體系的影響。通過對歷次選舉結果的量化分析，本研究發現香港選舉制度變革的後果既有符合經典理論的一面，亦有不符合的一面。制度變革造成政黨體系的分化、弱化和激進化，也在一定程度上限制了香港政治的發展。 The electoral system in Hong Kong had experienced significant changes in past decades. The electoral system of geographical constituencies in LegCo had been changed from “double-seat, double-vote” to “single-seat, single-vote”, and then proportional representation. The purpose of this study is to analyze the political effect of electoral reform, especially its impact on the party system in Hong Kong. By quantitative analysis of electoral results, it is found that there are effects according to classical theories, as well as different characteristics. The reform of electoral system had led to fragmentation, weakening, and radicalization of party system, and confined political development in Hong Kong.