鄭和下西洋是中國航海史上著名而有代表性的事件，然而許多相關的迷思、誤解、偽造等常會透過媒體影響公眾對歷史真相的瞭解與判斷，以及妨礙科學與歷史的研究。本文整理分析有關鄭和航海在破紀錄、寶船、航行方面的迷思，澄清鄭和的航行並非探險性的官方航海，沒有打破任何中國海上開拓的紀錄，而且明史中記載的寶船長44丈4尺的尺寸可疑，但仍為懸案未決，相關的船隻與寶船的比較及其他航海事蹟與鄭和航海的比較也有不當與誤導之處；而對如果鄭和繞過好望角的推想也多流於不切實際的想像，且常為層層假設的臆測，並無討論價值；同時也為藏匿鄭和航海檔案的劉大夏平反，指出其思考是在正常國情下的理性決策，而非愚蠢短視之舉。本文並指出許多迷思產生的動機與名、利、民族主義、政治利益有關，特別是最近又成為中國政府應付中國威脅論及對台灣工作的工具。最後，本文建議以「明初宦官使西洋」取代「鄭和下西洋」，以提供一個完整的、非英雄式、非民族主義式的公共印象來修正過去的迷思與誤解。

Zheng He's voyages in Southeastern Asia and India Ocean was a significant event in China's maritime history. There exists many myths, misunderstandings, and even lies broadcasted through mass media and affecting general public's understanding and judgment of history. This article analyzed and summarized myths about record-breaking, Treasure Ship, and sailing of Zheng He's fleet in early Ming dynasty. It is emphasized that Zheng He did not break any Chinese maritime exploration record, and the treasure ship's dimensions are still suspicious and undecided. Many related comparisons between Zheng He and other sailings in history on ship, and record also have problems. Those thoughts about what if Zheng He reached Atlantic Ocean are criticized for simple and careless thoughts, guessing based on many levels of groundless assumption, and lacking of discussion value. The decision to stop such kind of voyages is judged as a normal and reasonable policy for the empire's economy and normal balanced development, instead of a wrong or stupid decision lacking of visions. In this article, the motives these myths are analyzed as related with fame, profit, nationalism, and political agenda. They also became a tool of Chinese government to soften the fears of a rising China and to politically work on Taiwan issue. Finally, it is suggested to rename a common Chinese phrase "Zheng He Xia Xiyang"(Zheng He voyaging to Western Ocean) to "Eunuch Ambassadors to Western Ocean in Early Ming" for a more complete, non-heroic, and non-nationalist public impression.