本文試圖研究影響縣市長選舉勝敗的因素，整理自1989年至2001年四次縣市長選舉中，有關政治環境、府際關係、地方經濟、治安、個人背景、政治版圖以及現任優勢等因素，來分析影響候選人勝敗的關鍵因素爲何，並將模型運用在2005年的縣市長選舉結果來做檢驗。作者發現，主要政黨提名和現任優勢是影響縣市長選舉的最主要因素。擔任過省議員和立法委員的資歷也有顯著幫助。另一方面，影響現任縣市長能否連任的最主要因素，則是其上一屆當選時，得票率有無過半，顯示政治版圖因素在縣市長選戰中的重要性。 This article attempts to study the keys affecting county magistrate (city mayor) elections, accumulating potential factors across all elections from 1989 to 2001, including political environment, governmental relations, local economy, crime rate, candidate personal background, political landscape, and incumbent advantage, etc. We hope to identify and built a model of electoral success, and apply the model on the 2005 county magistrate election to check its validity. We found that nomination by the two major parties and incumbent advantage are the primary factors affecting the results of county magistrate elections. Experiences as legislators and provincial legislators also have significant positive influence on winning. On the other hand, the main factor affecting an incumbent county magistrate's chances of reelection is whether he or she got majority support in his or her first term. This shows the importance of political landscape on county magistrate elections.