本文試圖從所建立的現代漢語外來語語料庫中分析現代漢語外來語中聲調角色的音韻意義。漢語是一聲調語言，其聲調為辨義的必要成分。語料中看到漢語外來語在對應來源語的重音時，主要以高聲調來對應主重音位置，而非主要重音位置則不優先選擇高聲調對應，此乃聲調中音高音長直接影響重音聽覺認知的音韻意義。在優選理論架構下，是優勢對應制約、聲調必要制約、優勢單位連聲調制約等，透過制約交錯排序篩選，而顯出外來語中聲調對應重音的處理過程。其中優勢對應制約是說明優勢單位必定要顯出來，故以高聲調對應之。聲調必要制約是針對漢語的音韻系統要求，也是指外來語受到借入語系統的限制。而優勢單位和聲調相組的制約層級，是針對優勢單位聲調的選擇，要讓優勢單位顯明出來，連高聲調使其音高較高，音長較長，相對之下，其他非優勢單位的聲調便弱化，音高略降音長略短，便有烘托優勢單位的效果。以上所述制約是存在於普遍語法的，可以從其他語言的外來語看見這些相關制約的影響。

The main focus in this paper is to analyze the tonal phenomena in Taiwan Mandarin-Chinese loanwords, in the Optimality-Theoretical framework. Firstly, we set up a corpus of loanwords and observe the mapping between stress and tone. Tone is obligatory in Chinese grammatical words. Every loanword must have a tone. However the source language, such as English has stress, instead of tone. The loanword data show that the high tone is preferred to map the stress unit, and the unstressed unit is not preferred to map a high tone. The proposal for analyzing the tonal phenomena in loanwords is that the prominent unit in every language must be parsed in the surface forms. The prominent unit in English is realized as a stressed syllable. Tone is a phonological unit to be parsed in Chinese loanwords. The decision of tones of Mandarin-Chinese loanwords is proposed to be according to the ranking of relevant constraints such as Faith-Prominence, Tone-Obligatory, *Prominence/L, *PProminence/M, *Prominence/H. Moreover, some part of loanword data show that the stressed unit is realized as a non-high tone and the unstressed unit as a high tone. The part of data would be proposed as to be lack of common or suitable writing characters and not to violate Mandarin phonotactic constraints.