從語言的含意層面來說，由於「慣用語」包含了社會文化意涵的特殊性，要精通目標語之慣用語在外語學習者來說，實為不容易，因為其釋義並非完全取決於單獨字義的分析與連結。然而，當外語學習者如能在目標語的學習上增加其慣用語知識，他們自然能夠更適切地使用目標語，而使他們的外語能力與程度都相對的提升。本研究的目的是要探究台灣目前大學學生對英語慣用語的熟悉度及其理解過程，研究問題共有以下幾個方向：（1）大學生的英語字彙量是否影響他的慣用語理解？（2）大學生的英語字彙量是否影響他對於含有慣用語的閱讀理解？（3）學生的慣用語理解程度是否影響他的閱讀理解能力？（3）學生對於學習英語慣用語的普遍態度為何？一百零七位南部某大學應用外語系大二學生參與本研究。研究設計採用混合型之研究方法：量化與質化兩種研究方法都將使用於本研究，包含資料收集及統計工具的分析。研究結果發現，學生的字彙量和慣用語程度皆與其之閱讀理解能力有正向相關性，且皆達到統計上之顯著相關。大多數學生對於學習英語慣用語普遍皆表達正面態度及重視其必要性，高達91.6%認為增加慣用語知識能提升其英語能力。在贊成應將慣用語教學融入學校英語課程的支持者中，65.4%主張在初級課程就要教，然而有20.6%認為延至高階課程再教。在匯集自學生「有聲思考法」（think-aloud）的研究資料中，對於學生在理解慣用語的問題及困難，有更深入的了解。最後，研究者就教師在英語教室中提升慣用語教學應用，在結論中提出建議。

Since idiom embraces its specific social-cultural implication of the language, mastering idioms is hard for L2 learners since the meanings of the texts cannot be determined through an analysis of their individual word meanings. However, when EFL learners' idiomatic knowledge is developed, subsequently enabling them to use the language appropriately, their proficiency is definitely enhanced. Thus, the purpose of the study is to investigate college EFL learners in the following aspects: (1) how learners' vocabulary size impacts their idiom comprehension, (2) how learners' vocabulary size impacts their ability in reading comprehension with idioms, (3) how their idiom proficiency affects their reading comprehension ability, and (4) what their comprehending difficulties and general learning attitudes are toward idioms.One hundred and seven sophomores majoring in English at a southern private university participated in this study. The mix-method approach was used for the research design. The findings reveal that learners' vocabulary size and their idiom proficiency, learners' vocabulary size and their ability in reading comprehension, and learners' idiom proficiency and their reading comprehension ability were all positively related, and all of them reached a statistically significance. Regarding learners' attitudes, the majority presented a positive attitude toward idiom learning and also valued its necessity. Most of them agreed that acquiring more idioms can improve their L2 proficiency (86.9%), and 91.6% believed that their idiom knowledge should be enhanced. Among the advocates who stood for integrating idiom teaching into EFL courses, the majority argued that idioms should be taught at the beginning level (65.4%), and 20.6% claimed it should be waited until the advanced level. Some pedagogical implications for classroom teachers to improve idiom teaching in EFL contexts are also included.