在遠距教育的研究中，學習成效的探討一直是相當重要的議題，然而過去的研究多僅評估不同傳播媒體的有效性或比較近、遠端學生學習成效的差異，缺乏對於學習成效之發生歷程的探討。本研究根據Moore（1993）所提出之互動性距離理論，探討在同步遠距教學環境下學習成效之發生歷程，研究目的如下：一、對話、結構是否能有效預測互動性距離；二、學習者自主性是否能調節互動性距離與學習成效之間的關係。本研究採問卷調查法，受試來自四所大學修習遠距課程的學生，有效樣本239人。研究結果顯示：一、對話與結構可以有效預測互動性距離；二、互動性距離越低，主、客觀學習成效指標表現越好；三、學習者自主性可以調節互動性距離與主觀學習成效指標之關係（當學習者自主性高時，越低的互動性距離可以預測越高的滿意度），然而，學習者自主性不能調節互動性距離與客觀學習成效指標之關係。 本文最後針對所有研究結果進行討論，並根據研究結果提出可能的限制與未來研究方向的建議。 / The learning performance of distance education has been studied for a long period of time. Most of the past studies just simply compared the effectiveness of different media and teaching styles or the learning performances of students in local and remote site. However, little empirical studies had been found to see the process underlying learning performance. As mentioned above, a framework of the process underlying learning performance in synchronous videoconferencing learning environment based on the theory of transactional distance (More, 1993) was developed in this research.239 subjects from four different universities involved in the current study. The result showed that, first, dialogue and program structure could successfully predict the degree of transactional distance. Second, the smaller the transactional distance was, the better the objective and subjective learning performance was. Third, learner autonomy could moderate the relation between the transactional distance and the subjective learning performance. When students’ learner autonomy were high, the smaller the transactional distance was, the better the subjective performance was. However, learner autonomy couldn’t moderate the relation between the transactional distance and the objective learning performance.