本研究旨在探討以中文為母語之人士如何學習英語條件句，及其在習得時所遭遇之困難及相關原因。本文除對英語條件句之分類方式做詳盡介紹外，並嘗試以形式功能對應之理論架構，研究其習得之順序，並利用『錯誤分析』區分出條件句之動詞各類錯誤的誤用形式及原因。本研究語料來源為包含一百萬字，以電腦輔助建立錯誤標記之『中國學習者英語語料庫』。 研究結果發現，外語學習者之習得順序為一形式功能對應之過程，具較多形式或功能內涵者愈晚且愈難習得，符合功能認知模式的預測。 中文學習者的錯誤特徵為添加及省略，原因為過度矯正(hypercorrection)及過度類化(overgeneralization)。學習者最大的困難來自對條件句動詞變化規則不熟悉、形式及功能的複雜性、以及對應失敗的結果。本論文建議未來研究方向可深入探討時間指涉與假設程度對條件句使用之影響。 / Issues of conditionals have been highlighted for a long time, but the focus was seldom fixed on acquisition, particularly for L2. The determinate features of tense, mood and modality are interwoven in the conditional construction, thus resulting in an insurmountable obstacle for L2 learners. However, the factors impede acquisition have never been satisfactorily treated. Therefore, this paper attempts to explore the L2 developmental sequence, and to probe the error characteristics of acquiring if-conditionals. Disengaging the expression of conditionality into two dimensions: temporality and hypotheticality, we identified the features of syntactic forms and semantic functions of different conditional types, and created a new scheme to account for their mapping, on which the difficulty levels of acquisition were inferred. In contrast to the previous studies on the grounds of markedness theories, this research described the acquisition of conditionals in a Functional-Cognitive Model. Furthermore, the factors of difficulties were examined via an error analysis. The targets are Chinese English learners, who were well-known to face great problems in expressing conditionals. The data was searched from CLEC (Chinese Learner English Corpus), a big-scale corpus consisting of roughly 1,000,000 words with error tags. The investigation on the acquisition sequence and error patterns shows: (1) the acquisition order parallels to the prediction on the form-function mapping underpinnings: those with heavy content load and complex lexical shapes are acquired later (2) the two prominent misuses of the Chinese learners are addition and omission, resulted from hypercorrection and oversimplification. It was concluded that their difficulties could be ascribed to unfamiliarity of rules, complexities of forms and functions, and their mapping failure. Hence, this present work serves to provide some explanatory accounts, in a hope to unveil the mystery of the arduousness of acquiring conditionals, contribute to the tightening of acquisition theorizing and shed new insights into pedagogical growth.