本篇論文從語料庫及優選理論，分析台語中的日語借字，探討兩個語言之間的音韻調整現象。 本研究建立一個日語借字語料庫，以數據資料佐證音段替代的趨向，釐清音段替代的主要性和次要性。統計發現，單一日語音段，雖然可能被不同的台語音段取代，但由於比例差距的懸殊，日語和台語音段的對應情形，大多可視為一對一的關係。至於一對二的對應情形，則可歸因於台語音韻限制，或是對於借字和來源字之間音徵保留的要求。 基於語料庫的數據，本篇從優選理論分析日語和台語間的音韻調整現象。音段替代方面，主要歸因於IDENT[feature]，MAX，以及結構性制約(markedness constraint)之間的排序部署。另外，文中提出四個並存音韻，藉由調整MAX和IDENT[MR]之間，以及SHARE[back]和IDENT[anterior]之間的排序，解釋日語借字中的自由變異(free variation)現象。最後，受到IDENT[μ]和*[μμμ]的控制，相鄰兩個音節不會合併為一個，如果合併後發生音拍(mora)數量刪減或增加，或是產生一個含有二個音拍以上的音節。 / This thesis investigates the phonological adjustment of Japanese loanwords in Taiwanese. A corpus is established, and the statistics are provided to observe the substitute tendency of each of the Japanese sources. The use of the statistics properly explains whether a corresponding Taiwanese segment is either a regular substitute or merely an exception. Most of the Japanese segments are in one-to-one mapping when they are borrowed into Taiwanese. Some Japanese segments are in one-to-two mapping, due to either Taiwanese phonotatics or feature preservation between the sources and the loans, such as the phenomenon of reconfiguration. Besides, two adjacent syllables will combine to one, if the vowels are syllabified as a VG sequence after combination; in that event, the second syllable does not end with a nasal coda. Moreover, a glottal stop will insert to a word-final position if the penultimate syllable in a loanword ends with a vowel or a non-sonorant consonant. This analysis, based on the corpus, is conducted under the framework of Optimality Theory (Prince and Smolensky 1993/2004). For segmental substitutions, a set of IDENT[feature] is adopted to require the identity of certain features. The markedness constraints, regarding the segmental and place markedness and the Taiwanese phonotatics, are employed. High ranking of markedness constraints are responsible for adjustment of segments. Besides, re-rankings of SHARE[back] and IDENT[anterior] and MAX and IDENT[MR], are suggested. They are responsible for the substitutes that are in free variation. As for the contraction of syllables, it allows the loans and the sources to have the same numbers of moras. However, contraction is suspended, to prevent a syllable to have three or more moras.