二元行政是半總統制與總統制、議會內閣制相較之下，最具差異 性，也是影響半總統制實際運作最核心的一個制度環節。實務運作上， 二元行政依據本質可以有很多的比較視野，在分權的模式之下，總理 可能和總統分工合作，也可能呈現上下的僚屬關係。據此並進一步影 響二元行政和立法權的互動與結果。依據台灣過去的經驗，總統與行 政院院長無論所屬政黨在國會是否享有多數，都是維持一致性，且行 政院長從屬於總統的二元行政關係。但仔細觀察歷任行政院長，可以 概略分爲政黨資歷豐富或是官僚資歷豐富的不同類型。本文將先針對 行政院長的背景，區分爲政黨菁英與官僚菁英兩種類行，再據此探討 其形成的背景以及在與立法權互動後所產生的影響。

The dual executive system is the most significant institutional characteristic of semi-presidentialism. In practice, the President and the Prime Minister may cooperate or compete with each other. The process and outcome of lawmaking will also be different with different types of dual executive system. Since Taiwan adopted a semi-presidential constitution in 1997, the President and the Prime Minister have always been from the same camp whether the ruling party enjoys parliamentary majority or not. However, the prime ministers can be classified into two different types, namely party elite and bureaucratic elite. This paper tries to discuss the influences that different types of prime minister have on legislation. This paper will first define and classify the two different types of prime minister and then compare the various influences they have on legislation.