There are few literatures to explore political party¡¦s Nomination Institution and its relationship with electoral system. This thesis traces Legislative Yuan elections system from multi-member-district, single non-transferable vote to single-member district with plurality system and single-district two votes system and explore whether the modification has had an impact on party¡¦s nomination institution. According to theoretical assumption and foreign research statistics, ¡§single-district two votes system¡¨ tends to promote political party nomination system towards top-down decentralization. This study aims to investigate whether single-district two votes system is able to influence political parties to improve the centralized nomination institution that had been rooted in SNTV. The findings are positive regarding the application of single-district two votes system. During the seventh legislators election, major Parties of R.O.C. had adjusted their Nomination Institution, and Party members¡¦ opinions along with public¡¦s preference had been taken into accounts greatly compare to the past. KMT is one of the salient examples for not only make the largest modification in nomination, but also gain the most profit from this election.